Re: [time-nuts] Racal 9475 Rubidium
Hi, There's a copy of the manual at: http://www.ko4bb.com What are the symptoms? Angus. On Tue, 1 May 2018 10:18:35 +0100, you wrote: >Hi all new member hear could any of you help with the following information > > > >As I have just bought a Racal 9475 Rubidium and it has problems > > > >Is there any stock faults ? > >What is the life of the rubidium standard? > > > >Regards Paul > >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom 58532A GPS Antenna : Launch3 Surplus
Hi, The problem is that because of the type and position of the connectors on so many of the Trimble, Novatel, etc., antennas, it's practically impossible to seal them with something easily removed like self amalgamating tape. Antennas like the 58532A make life a lot simpler by hiding the connector up a tube. The idea seems to be that nickel plated brass TNC connectors are all that's needed, but it's not that simple - particularly for coastal or marine use. In fairness, even a lot of manufacturers of dedicated marine gear vastly underestimate where water can get to and what damage it will do - at least they did back in the 1990's when I was working with that stuff. It could take a very long time (if ever) for them to be convinced that what works in their nice little environmental test chamber could possibly fail out in the big bad world! >However, for the past 10 years or so I have been using double wall >adhesive lined heat shrink tubing. My local electronics and electrical >supplies carry this product and it is not that expensive. This I find >both quicker to install, neater, more reliable, and much easier to >remove than the rubber tape followed by vinyl tape method. I was not convinced about adhesive lined heat shrink when I tried it since it usually didn't seem to bond well enough to withstand bending, although I've not tried the newer types. It probably wasn't the premium quality tubing Adrian mentioned either. The PIB based self amalgamating tapes had to be well taped up and did not like oil, but the EPDM and PE ones we used were less sensitive although they still needed to be taped up. Since I wanted to be able to swap them easily, I eventually got some Amphenol ARC TNC connectors for the GPS antennas, but still chickened out of using the heat shrink supplied and went for self amalgamating tape instead for sealing the crimp. I really should try the unused heat shrink on something to see how it does. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom 58532A GPS Antenna : Launch3 Surplus
On Tue, 6 Feb 2018 14:54:23 -0500, you wrote: >3) its designed for continuous outdoor use (connector is well shielded etc) That's something that has always baffled me - the number of antennas which the manufacturers claim are suitable for long term outdoor use that have connectors which are impossible to seal without large quantities of sealant or whatever. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TAPR "PulsePuppy" Pot Selection
Hi, Normally it's best to adjust a multi-turn trimmer in just one direction, so if you do overshoot, go back 2 or 3 turns and then on again to the place you want to be. The imperfections in the mechanism will drive you nuts (in a bad way) if you try to do fine adjustments back and forth. It's even better if you can monitor the wiper voltage when adjusting it. Angus. On Sun, 24 Dec 2017 16:26:43 -0600, you wrote: >I think I need to clarify what I mean by "backlash". It is not simple free >play in >the adjustment mechanism- it is something much more irritating, as follows: > >I sneak up on the desired result, but manage to overshoot slightly. So I back >off on the screw, and find that at first the result continues to change in the >*original* direction (making the overshoot even worse) for a bit before finally >reversing as I wanted it to. This behavior is not conducive to having a good >time making critical adjustments, nor does it lend any confidence in the >stability >of the adjustment in the face of handling. > >Dana > > >On Sun, Dec 24, 2017 at 4:06 PM, Charles Steinmetz <csteinm...@yandex.com> >wrote: > >> John wrote: >> >> I didn't really notice much backlash, though when setting oscillators I >>> try to approach (slowly) from one direction until it's "good enough" and >>> then stop, to avoid that problem. >>> >> >> The hot tip is not to just "sneak[] up on the sweet spot and then walk[] >> away," as Dana put it. >> >> Anytime you have an adjustment with some hysteresis (classic example is >> setting a d'Arsonville movement to zero), you want to sneak up to the >> perfect setting and then run the adjuster *back* the way you came just a >> touch, to leave the adjusted part on its own without any mechanical >> connection to the adjustor mechanism. Such contact is almost always the >> culprit if the adjustment drifts after you set it. >> >> This takes some "feel" for the motion of the adjuster mechanism, but it is >> well worth investing the time to learn it by repeated trials of the >> adjuster before you leave it alone. >> >> Dana is spot on with his advice to tap the board (or whatever mechanically >> supports the adjusted part) to make sure it doesn't drift. If it does, you >> either failed to pull the adjuster out of contact with the moving adjusting >> part, or the adjusted part just can't hold its setting. In either case, >> better to know that now than after you button the instrument back up. >> >> Best regards, >> >> Charles >> >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3
That near the end of the temperature range the direction could also give a good indication - assuming that there is only one problem... I think the 8600-3 is still an AT - the 8607 is SC. Angus. On Fri, 8 Dec 2017 15:40:08 -0500, you wrote: >Hi > >One basic question - Is the frequency high or low? > >Assuming its an SC and on the lower turn, frequency low is possible >with an off temperature oven. Frequency high is unlikely unless its *way* >off temperature. How far off turn gives you how much delta F depends on >the inflection temperature of the crystal. It matters if its a true SCor a >modified SC .. If it is a true SC and running at 80C, thats about 10 degrees >below inflection. There will not be a lot of frequency change in that case. > >Many (but not all) modern crystal processes tend to age positive. If that is >the >case on these parts, a frequency high is the likely outcome of age out of >range. >Even with a process that has a known tendency, only about 70% of them go >that direction over long periods of time. Its not a perfect thing . > >Bob > >> On Dec 8, 2017, at 2:34 PM, Angus <not.ag...@btinternet.com> wrote: >> >> >> The 8601 that I have was about 2 deg C off turnover when I got it, but >> I can't remember what sort or frequency error that caused. The >> temperature coefficient was terrible with that error. >> >> Angus. >> >> >> On Fri, 8 Dec 2017 13:05:14 + (UTC), you wrote: >> >>> >>> Gentlemen, >>> We have an Oscilloquartz OCXO 8600-3that cannot any longer be adjusted into >>> 5,000,000 Hz.It is about 1 Hz out of 5 MHz and turning >>> coarse/fineadjustment potentiometers cannot bring the frequencyinto its >>> specification. >>> Oven temperature is about + 80C accordingto the thermistor and the >>> operating voltageis at 24 VDC. >>> Have Googled but the only thing that turns upis datasheets w/o any details. >>> Before I take it apart and start lookingfor obviously broken components, >>> isthere anyone that has a CLIP on this unit? >>> 73 >>> >>> Ulf Kylenfall - SM6GXV >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3
The 8601 that I have was about 2 deg C off turnover when I got it, but I can't remember what sort or frequency error that caused. The temperature coefficient was terrible with that error. Angus. On Fri, 8 Dec 2017 13:05:14 + (UTC), you wrote: > >Gentlemen, >We have an Oscilloquartz OCXO 8600-3that cannot any longer be adjusted into >5,000,000 Hz.It is about 1 Hz out of 5 MHz and turning coarse/fineadjustment >potentiometers cannot bring the frequencyinto its specification. >Oven temperature is about + 80C accordingto the thermistor and the operating >voltageis at 24 VDC. >Have Googled but the only thing that turns upis datasheets w/o any details. >Before I take it apart and start lookingfor obviously broken components, >isthere anyone that has a CLIP on this unit? >73 > >Ulf Kylenfall - SM6GXV >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Recommendation for cheap GBIP adapter for Linux
On Sat, 18 Nov 2017 20:21:13 +, you wrote: >The Galvant adapter appears to use a very similar protocol to the Prologix, >but I'm unsure if it's exactly compatible. > >There have been large numbers of HP adapters on ebay - they're generally >thought to be clones of varying quality. > >http://www.galvant.ca/#!/store >http://www.eevblog.com/forum/testgear/flood-of-new-agilent-82357b-gpib-usb-adaptors-on-ebay-the-real-deal/150/ > Hi, The commands in the Galvant one do seem to have been done to be quite like the Prologix. I tried one of them 2 or 3 years ago because they were temptingly cheap at the time, but could not get it working consistently. As far as I can remember, single commands and short strings would often work for me, but longer strings and regular data like readings every second were very unreliable. They seem to work for some folk but not for others, which is often the story for cheap low volume ones. In the end I gave up and bought a Prologix - which appears to be a common end result of buying and wasting time on cheaper ones. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Input filter for data logger
On Sun, 19 Nov 2017 16:10:54 -0500, you wrote: >> The MV89 is a beast of an OCXO and uses more power at warm-up than any >> other >> I know of. But it is spec'ed ~1W for steady state. Which means the >> outside of the OCXO should be about hand-warm. If it's too hot, then >> the heater circuit is probably broken and running at full-throttle. > >If so, I think something is not OK with my MV89. It is probably 110 >degrees or so. They do run hot, so if that's 110 DegF and not DegC it's OK (depending on ambient...) The data sheet says 4.2W at 25 DegC. BTW if anyone is thinking of visiting www.morion.com.ru this might not be a good day - when I tried earlier the AV claimed it was infected and the script blocker went nuts, so they did seem to have got infected by something. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] RS232 output on a 53181A
Hi, Also, since it's a p rather than any other character, my guess is that it probably was deliberate - although whether it was meant to be shipped like that is another question. Angus. On Wed, 12 Jul 2017 11:56:24 -0400, you wrote: >Well ASCII * is 2a in Hex, p is 70 so that seems an unlikely substitution >for a failing EPROM. > >But 0 is 30 Hex, only one bit different from p. > >On Wed, Jul 12, 2017 at 10:39 AM, Angus <not.ag...@btinternet.com> wrote: > >> Hi, >> >> I've just been using an Agilent 53181A, but the serial output is not >> quite what I had expected. On the 53131A's that I've used the >> placeholder character on the RS232 output is an asterisk, but with >> this unit it is a lower case 'p'. Where the 53131A sends '2,*** u', >> this 53181A send '2,ppp u'. The only references to a placeholder that >> I saw in the manuals referred to an asterisk. >> >> The firmware version is 4613. >> >> Anyway, just wondering if anyone knows if this is correct, or maybe >> it's just the EPROM starting to fail. >> >> Thanks, >> Angus. >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >> and follow the instructions there. >> ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] RS232 output on a 53181A
Hi, I've just been using an Agilent 53181A, but the serial output is not quite what I had expected. On the 53131A's that I've used the placeholder character on the RS232 output is an asterisk, but with this unit it is a lower case 'p'. Where the 53131A sends '2,*** u', this 53181A send '2,ppp u'. The only references to a placeholder that I saw in the manuals referred to an asterisk. The firmware version is 4613. Anyway, just wondering if anyone knows if this is correct, or maybe it's just the EPROM starting to fail. Thanks, Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] LPFRS phase ripple?
Hi, If you've not already looked, it would be worth checking on the EEVblog since there were some discussions there on faults in these units - particularly the capacitor and lamp voltage issues. One of the temperature controllers could be a little unstable too. Angus. On Tue, 23 May 2017 09:40:26 +0200, you wrote: >Hello Time-Nuts, > >i´ve been playing with some Rbs recently. > >I compared two LPFRS-01 to a PRS-10. One seems to behave quite well (compared >to the specs given here: >http://www.spectratime.com/uploads/documents/isource/iSource_LPFRS%20Spec.pdf) >- short term stability specs are met), the other one shows quite some phase >ripple (appx. 1 ns RMS with a frequency around 0.007 Hz) which spoils ADEV in >the 60 - 200s range, very similiar to the typical GPSDO bump. Long term >stabilty is OK. > >Unfortunatly I didn´t find any schematics on the web. Has anyone encountered a >similiar problem with this unit? Any idea were this might come from? My first >guess would be a problem in the control loop locking the VCXO to the Rb, but I >have no clue which time constants are used in the PLL. > >Any hints are appreciated. > >Regards, > >Matthias > >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Three-cornered hat on timelab?
Hi Bob, This is a phase plot of a rubidium to an M12 from a test that I did back in 2008. The offset and ageing have been removed, but there is still a bit of wander. As with your plot, constellation related issues appear the most obvious. Peak to peak is fairly similar too. Angus. On Thu, 27 Apr 2017 16:48:37 + (UTC), you wrote: >Hi Magnus, >Try as I might, the weather and the local power company had other ideas about >my long term capture. I'm running everything but the 5370 from a UPS. I >guess I'm going to have to get batteries for my other UPS and run the 5370 >from that. A one second power loss was all it took to stop the test. > >Anyway, I did manage to get 376,238 points of data. The data is captured on a >5370A. The external clock input and the STOP channel are fed by the 10MHz >from my PRS-45A. The START channel is fed by the 10MHz from one of my GPSDOs. > The EXT channel is fed by the 1PPS from another of my GPSDO units. "EXT ARM" >is enabled. So, essentially, at every 1PPS pulse, the phase difference >between the two 10MHz feeds is captured. > >I've attached a screenshot of the phase plot which can also be found >here:http://evoria.net/AE6RV/Timelab/Screenshot.png >I've also made the timelab file (compressed by 7z) available here: >http://evoria.net/AE6RV/Timelab/GFSvsCS.4.22.17.7z > >So, back to my question: Where are the large ionospheric phase moves? This >question has been causing me doubt since I started on this project. Or don't >I still have enough data collected for this to happen? > >Bob > >- >AE6RV.com > >GFS GPSDO list: >groups.yahoo.com/neo/groups/GFS-GPSDOs/info > > From: Magnus Danielson <mag...@rubidium.dyndns.org> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency > measurement <time-nuts@febo.com> >Cc: mag...@rubidium.se > Sent: Tuesday, April 18, 2017 1:09 AM > Subject: Re: [time-nuts] Three-cornered hat on timelab? > >Hi Bob, > >That is a good solution indeed. Good luck with that measurement run! > >One of the fun stuff with Timelab is that you can walk by and check the >developments. I've found that very useful for long measurements (as in >hours and days). > >I prepared a cesium for one vendor, and initially they did not care so >much, but then they saw more deviations between the receivers, so they >wanted to sort it out, but discovered that they could not cancel out the >common mode of GPS signals (and its shifts), so then firing up that >cesium was the right thing. I remember writing support emails while >waiting for the airplane in Madrid airport, happy that they was doing a >first run for the right measurement reason. :) > >Cheers, >Magnus > >On 04/18/2017 04:25 AM, Bob Stewart wrote: >> Hi Magnus, >> Today I started a long run against my PRS-45A. Maybe this time I won't have >> a power outage. I'll see what it tells me in a few days. >> Bob > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Time Dilation tinkering
On Tue, 21 Mar 2017 13:08:56 +0100, you wrote: >On Tue, 21 Mar 2017 13:38:51 +1100 >Hugh Blemings <h...@blemings.org> wrote: > >> This got me to wondering if a Rubidium based standard might do the trick >> - the Efratom SLCR-101s seem readily available for ~USD$200 mark. > >As TvB wrote, a single one will not do the trick. You will need >a stability 1e-14 @1d. IIRC most Rb standards floor out at 1e-12 to 1e-13 >somewhere between 1k and 100k seconds. Even the Super-5065 has a floor >of about 3-4e-14 (unless our friends here improved on this already). > >There will be a few things that you will need to do, if you want to go >with Rubidiums: >1) Stabilize or compensate for environmental effects (temperature, air >pressure) >2) Build ensembles of Rb clocks. > Hi, Looking back at an old plot I did of a temperature controlled and air pressure compensated LPRO against an M12+T, the Hadamard Deviation of the 1000s averages of the 1PPS measurement was about 5E-14 at 1 day. A large part of that was likely the GPS, so with a better rubidium like an FRK-H in a sealed and temperature controlled enclosure you might be around 1E-14 at 1 day. The bit that I'm not so sure about is the travelling. A long period of movement, vibration, magnetic fields, etc. all adding in could obscure the effects of time dilation. It might be quite possible, although a nearby mountain and a friend with a helicopter would make it a lot easier! Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How to create a super Rb standard
> It looks like their is as infinitely small chance of being able to get 5065. > So what can be done with the telco Rb's (mine are analog tuned) to > wring the best possible performance from them? Sooper Duper power > supplies, Peltier (sp) cooling modules? > Regards, > Perrier Hi, I'm always a bit surprised that it's not done more. Adding temperature control, air pressure compensation and drift compensation transforms the medium to long(ish) term performance of a lot of rubidiums. A typical Adev plot for a rubidium starts increasing again after a few 1000's of seconds as environmental factors take their toll, but with even a simple version of these mods it's more like days. This makes it a great reference for testing GPS receivers and GPSDO's among other things. A basic setup could be something like an LPRO in a temp controlled enclosure, with an analogue pressure sensor feeding into an EFC circuit, both temp controlled with the LPRO. Log it against GPS and you get the long term (like weeks+) ageing which can then be removed. Even simpler, you could just log the air pressure and correct for that too, but that's more of a pain if it's being used as a general purpose reference. Of course, the problem then is testing just how good it is Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] hm H Maser
On Tue, 10 Jan 2017 21:43:07 -0500, you wrote: > >This does get back to state of the art Rb and what that means. In my >suggested case thats measured in terms of ADEV for Tau = 1 to 1,000,000 >seconds. If you wanted an Rb with (only) state of the art phase noise at 1 MHz >offset thats a different thing. State of the art for >power consumption and size is also not what Im suggesting in this case. Why >the choice of spec? this is TimeNuts. Hi, Some discussions on the performance that might be practically achieved with different designs may be a useful start - as long as it's done in the context of a practical unit that could actually get built, rather than just a theoretical wish list. It would also be good to have some idea of the cost of any special parts like cells too. Without that info, it's hard to know how practical particular designs would be. Looking at export/technology controls might be useful early on too, since we're going for high performance. I've often wondered how a 21st century version of a 5065 would perform, so it's great to see that I'm not completely alone in my insanity! Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Austron 2010B Manual.
Hi, I know this has been asked about a few times over the years, but I've not been able to find any user or service manuals for an Austron 2010B to download anywhere - anyone know of any? Thanks, Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ADC sample voting algorithm?
Hi, You may have already done this, but if you log the same pulses with a counter or actual TDC IC you can view it and see how they compare with your measurements. Then you can look at how to get them closer - or find that it's actually correct and that's just where the pulse is at the time. Angus. On Wed, 5 Oct 2016 16:45:21 -0700, you wrote: >This is tangentially on topic, I suppose. Its for my GPSDO. > >I notice periodically that the phase measurements seem noisy. You can see >that over the course of several seconds the value doesnt change, then it >jumps a bunch and then comes right back. > >My theory at the moment is that sampling the ADC multiple times in a row might >help, but then whats the best way to (quickly) pick which sample to use? > >The mean would allow a bad sample undue influence. > >At the moment, Ive coded taking 3 samples, averaging them and picking the >sample that is closest to the mean. If Im right, and two of the samples >happen to be very close to each other and a third is an outlier, then that >seems like it would eliminate it. > >I guess what I want is the mode, but with 3 samples, thats going to be poorly >defined (if at all). > >Anyone have any suggestions (besides a larger sample size)? >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Improving on basic L1 timing
Hi Michael, Thanks, that plot and the info gives a useful comparison. I think in light of everything, doing some tests with a generally upgraded setup would be the way to go for now. There would actually be several rubidiums, although initially with a bit of cheating - 1 counter, a 10PPS reference and a multiplexer. Later hopefully a separate TDC's though. I'm up in the north of Scotland, so unfortunately not much in the way of reference stations etc nearby, which does rule out some options. Angus. On Thu, 16 Jun 2016 17:53:39 +1000, you wrote: >I promised a plot and here it is. > >In a bit more detail: > >(a) "GPSCV 800 km baseline" is single-frequency transfer between two >5071s with standard tubes. I've divided by sqrt(2), assuming both >clocks contribute equally to TOTDEV. > >(b) "std tube spec" is from the 5071 manual, for comparison > >(c) "sawtooth corrected pps" is Javad receiver + std tube 5071 > >(d) "PPP solution" is precise point positioning (carrier phase) clock >solution, setup (c) but with a receiver which takes external 1 pps and >10 MHz. The win here is that measurements are now made wrt your clock >with very high resolution (ten ps or so for carrier phase) and you >don't have the sawtooth correction introducing noise. >The reference timescale in the PPP solution is a zero-weighted mean of >visible SV clocks. > >(e) "CGTTS" is single frequency, modeled ionosphere in CGGTTS files, setup (c) > >As you can see, you get a factor of two going from the >sawtooth-corrected PPS to CGGTTS. You can get rid of some >ionosphere-induced stability in a common view comparison. > >You get another factor of two going to a carrier-phase time solution. > >So as I said, you have to work hard/spend big to get a relatively >modest improvement. > >Hope this helps. > >Cheers >Michael > > > > > >On Wed, Jun 15, 2016 at 4:21 PM, Michael Wouters ><michaeljwout...@gmail.com> wrote: >> I should have added, if you do all of the above, the improvement in >> stability over just using a sawtooth-corrected PPS is not all that >> spectacular, a factor of two or three. I'll post a plot of some data >> tomorrow. >> >> Cheers >> Michael. >> >> >> On Wednesday, 15 June 2016, Michael Wouters <michaeljwout...@gmail.com> >> wrote: >>> >>> If you followed the link to www.openttp.org and are wondering where the >>> software is, follow the link on the home page to GitHub and then look in the >>> Develop branch. The ublox branch is for the new '8' series receivers. >>> >>> Cheers >>> Michael >>> >>> On Tuesday, 14 June 2016, Michael Wouters <michaeljwout...@gmail.com> >>> wrote: >>>> >>>> Hello Angus >>>> >>>> If you have 3 rubidiums of similar stability + 3 counters, you could >>>> do a 3-cornered hat. >>>> >>>> Otherwise, GPS common view to a better clock may be an option. If you >>>> are reasonably close to a national standards lab, you might be able to >>>> use their time-transfer files to compare your rubidiums with their >>>> time scale - not everyone makes them publically available though. >>>> Otherwise, if there is an IGS station near you, you could use the >>>> station RINEX files and IGS clock solutions which are freely >>>> available. Many IGS stations have a H-maser as the local clock. But it >>>> may be just as good to simply use the comparison with GPS time >>>> inherent in the time-transfer file. >>>> >>>> The advantage of generating a time-transfer file is the possibility of >>>> then improving upon the various corrections broadcast by GPS, >>>> effectively repeating what the GPS receiver does to generate its >>>> realization of GPS time but with better data. >>>> >>>> With post-processing, the short to medium term (less than 1 day) >>>> performance can be improved a bit as you are suggesting when you >>>> referred to "atmospheric issues". Improved ionospheric models are >>>> available or if there is an IGS station nearby, for example, the >>>> measured ionosphere could be used. Other improvements can be had with >>>> good antenna coordinates and using final orbits in the processing. >>>> >>>> What can you use for your time-transfer receiver ? Some low-cost >>>> single-frequency receivers are suitable eg the Trimble Resolution T. >>>> The essential requirement is the availability
Re: [time-nuts] Improving on basic L1 timing
>Make sure you have good skyview (aka good geometry) and very little >multipath. Both effects can affect the precision of your solution >much more than the ionospheric delay variation. Main one is on the peak of a slate roof. Nothing else much higher around except a large sycamore tree. There's another antenna at the edge of the roof about 1.5m below the peak, close to one end of the house, and although it does give slightly poorer stability, it did not look to be by a huge amount when I checked it. The reason that I was particularly looking at the ionospheric delay was that the diurnal variation was quite pronounced. The rubidium and gps were both in temperature controlled enclosures. That does still leave the antenna, cable and splitter, along with the counter and PPS buffering. >If you live in continental Europe, then you will inevitabely have an >IGS station nearby. They are everywhere! :-) I think it's a few hundred km for me! >The only other thing I can think of is using multiple Rb's as reference, >measure their temperature, air pressure and drift against GPS. That actually is the plan. Most would also be temperature controlled. >Use all >this data to build a clock model (aka Kalman filter) that compensates >for temp/pressure/aging and measure the Rb under test against this ensemble. >But that's not something that already exists and is ready to use. That's just the sort of thing that was always the end goal for this project - control what can be, understand and compensate for what can't. The rubidiums are what I'm primarily interested in - the gps was originally there for a basic reference, as well as for long term drift correction. Thing is, since I don't have access to a H-maser or good cesium, I'm also trying to see how well I can get gps to do as a medium to long term reference. It may well be best just to run some ordinary timing receivers for a while, and use the rubidiums for the rest. By then I'd have a better idea what performance would be needed to be useful, and if anything available to me would do that. Another complication is that a lot of the old data I have was done with an M12+T without sawtooth correction. With filtering or averaging it's irrelevant medium to long term which is why I didn't bother, but it messes up Adev plots making comparisons with a lot of the data out there more difficult. Some tests with other receivers and corrected or sawtooth-free data would be a good start. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Improving on basic L1 timing
Hi, I'm planning to test some rubidiums again, but since Santa never did get me that hydrogen maser I asked for, I'm still stuck with ordinary gps timing receivers as a separate medium to long term reference. The atmospheric issues are probably the main ones I would like to get rid of, although the more errors removed the better. It does not have to be done in real time, but even an single test run would last weeks, so there could be a lot of data to tie together. It would really need to be something that actually exists rather than just an idea of how it might be done, since I really just don't have time for any more major projects anytime soon. I've found from experience that too much time spent making the test gear etc means that I don't get the time to actually use it! I'm also looking for something that's not too expensive - like up to hundreds rather than thousands of pounds. A good cesium or 2+ frequency gps with relevant options might be fine, but also rather out of my price range. BTW, I do plan on uploading the end results, in case anyone is interested. If anyone knows of some way to do this, (or even has something appropriate they want to sell) I'd appreciate hearing about it, on or off-list. Thanks, Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS altitude somewhat wrong?
I've had that query before too, but in that case it turned out to be that by default some receivers/software report Mean Sea Level and others Height Above Ellipsoid, or both. Angus. On Wed, 8 Jun 2016 20:33:58 +, you wrote: > >I have just installed a Thunderbolt here to get our time and frequency >equipment all on the same page. >As I was looking at the display on Lady Heather, I was noticing that the GPS >altitude seems rather wrong. >We are in Boulder CO, which is nominally 5430' and the antenna is about 20' >off the ground. >The display (near overdetermined position) reads 1589.72991 meters or 5216 and >change in feet. >Altitude is a big deal around here. :) > >I suppose 214' isn't that outrageous, but it does bring me to a question: > >How accurate is the altitude number really? > >Thanks. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Ublox Neo-6M time error.
I noticed that in 'Messages View' window in u-center, UBX-NAV-TIMEGPS
gives Time of week, but UBX-TIM-TP gives Time of next pulse, 1 second
later. The hex in the messages also differs by 1000ms.
Putting the correction data and the time of the next pulse together
like that would suggest that it is for the next pulse, but I've not
checked it with a counter.
Angus.
On Thu, 2 Jun 2016 08:28:58 +, you wrote:
>The Ublox receivers do not have a message that outputs GPS time directly.
>It's easiest to take the UTC time message and subtract the leapsecond offset
>to get GPS time. The itow value in the NAV_TIMEGPS message is milliseconds
>past midnight of the start of the GPS week... probably not something you want
>to be doing calculations from. I use the TIMEUTC message. I only use the
>leapsecond offset from TIMEGPS.
>
>It looks like Ublox is sending the time message AFTER the 1PPS pulse ("at the
>beep, the time was...") , and just about everybody else sends it before the
>pulse ("at the beep, the time is ...") ... Bastards! I wonder about the
>thought (or lack of it) process that decided that was the way to do it. And
>don't get me started on the idiot receivers that send the sawtooth correction
>message after the fact...
>--
>Despite re-checking I am still doubtful that my sums are right. Ill do a few
>more packets. Is this what you are seeing Mark?
>
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Re: [time-nuts] HP5065A environmental sensitivities
Hi Corby, That was really what I was hoping for from the small Rb's too, but there appears to be other things at work with them. I had not really considered that they might be sealed, but it's something to look at. I had been thinking more about how it was fixed into the package and with what materials. As well as the normal component and circuit issues, there are also some deliberate ones like discrete steps in temp correction which all add to the fun and confusion. BTW, if anyone has or knows of any pictures of a teardown of a FRK or LPRO physics package, I'd be very interested. Anyway, it's good to see that the 5065A is better behaved - I'm just more jealous now! I look forward to seeing the results of your tests. Angus. On Sun, 22 May 2016 08:58:16 -0700, you wrote: >Angus, > >The HP 5065A has a fairly open path from atmosphere to the cells as far a >barometric pressure is concerned. >Response is rapid to a change. > >The mechanism is "oil-canning" of the windows on the ends of the cell. >Depends on diameter of the cell, thickness of the windows, and stiffness >of the particular glass used. (for a particular gas mix of course) > >It is VERY repeatable, and VERY linear. > >I have heard that one European observatory routinely tracks the >barometric pressure by watching their 5065A shift. > >After seeing Wulf's data I can believe it! > >My circuit is eliminating that variable quite nicely. As others have >said, temperature will be a different matter. > >I'm currently doing temperature tests and plan to eliminate the major >causes rather than compensate. > >Early measurements show as-built to be better than the spec of >1.6X10-12/degree C. > >Cheers, > >Corby > >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Last Call Group Buy Ublox LEA-6T
On Wed, 18 May 2016 05:31:45 +, you wrote: >There is what looks like a decent carrier board for Ublox modules on >OSHPARK.COM's shared project library. It has a voltage regulator and RS-232 >interface on it... would be nicer if it had a prototype area and swoopty PPS >driver, but I'm too lazy to lay out a better one. Three boards will cost you >$30. >https://oshpark.com/shared_projects/8QR7ymk8 Just in case anyone thinking of it has not noticed - that one is for the smaller NEO version rather than the LEA version. So if anyone knows of a LEA version, or has one that they want to upload or whatever... ideally with sawtooth correction :) Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] MTI 260-0624-D OCXO
On Sat, 20 Feb 2016 14:56:47 -0500, you wrote: >I think that there are a lot of unexplored possibilities, but I definitely am >not convinced that it sets either the inner or outer oven temperature. There >are simply better ways to do that in production. Hi Mike, On the two that I tested, it appeared to adjust the temperature of both of the ovens. One was a 5 MHz 260-0545-B. The outer oven was at 78.2 degC and at least around that point the temp changed at about 1 degC per turn. The EFC adjustment on this one was not quite enough to bring the frequency to exactly 5 MHz, but the oven temp did look to be close to correct. The other was a 16.384 MHz 260-0546-G which was unused old stock, but had overall poor stability. It turned out that the oven temp on it was 1-3/8 turns from the turnover point, but when or how that happened I don't know. It would be interesting to hear from somebody who knows how this type of thing is actually adjusted in production. Angus. >> If this is a double oven, there are two oven circuits and two oven >> controllers. >> Both would have a set point and both would be adjusted somehow. The pot >> may be the adjustment on the outer oven. Get things all set up and packaged, >> then adjust the outer oven to make things do what the should do. > >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ACAM GP22 Chip
>I wouldn't expect the noise to >be in the ns range, but i wouldn't surprised if it was a few 10ps. >I have never done any measurements though, and I don't think i've >ever seen any jitter measurements for 32kHz oscillators, so take >this value as rough guestimate. On the GP21 board I used it was more like 10ns+. I don't know if that's typical, but it wasn't a even particularly cheapo crystal as the original one was faulty and I had to replace it. The official acam board might be better, but the data sheet specifically talks about the 32K osc having a lot of jitter. One of the problems of the data sheet is that it is really tailored for those using it as a flow converter - some of the text does not even make sense otherwise. That was one of the reasons I was planning to test it more as a TDC, but just getting back to doing that now. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ACAM GP22 Chip
Hi Thomas, Another option for generating a range of delays would be to use a stable oscillator like an ovenised one. This is actually similar to what the GP22 does for measuring on mode2. If you gate the output of the oscillator you can get a start and stops at 1us or 70us or whatever. It's useful because it allows you to test the whole measurement system rather than just the TDC noise which should be way below 1ns peak-peak. Angus. On Tue, 24 Nov 2015 14:04:32 -, you wrote: >Hello, > > > >I have an ACAM GP22 TDC chip and evaluation board which I am looking at for >work purposes I work for a company active in the weighing and force >measurement world. > > > >I should say from the start that I am new to time and frequency measurements >and not even an electronics engineer but then I have been exposed to >high-precision electronics for the last 25 years hence have picked up some >dangerous degree of half-knowledge. > > > >We want to use this chip to measure the period of a square wave, of around 13 >kHz i.e. in the 70 µs range. As the application is potentially high-accuracy >we need to know the period to within 1 ns or better. > > > >In order to evaluate the chip I was planning to replicate John As experiment >with the coaxial delay line from the HP5370b but as my interest is in >measuring range 2 of the GP22 I need a delay of 500 ns or more (actually 1 >µs sounds a better start). This is the equivalent of a 200 m length of cable. >I fear trouble with this: Am I not getting unwanted inductivities if I use a >coil of that size? > > > >So, to come to the point: Am I pushing the concept of a coax delay too far >with 1 µs and are there other (simple/reliable) ways to achieve this kind of >delay? I have tried it with a shorter piece of cable (around 2 ns which is >measured in range 1), there I seem to get consistency virtually to within >100 ps. But I need to know if the device sticks to this level of performance >when the periods are much longer, and thus measured in range 2. > > > >Thanks and best regards, > >Thomas. >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] PM6680 or 53131A for TimePod
Hi, PM6681's turn up at quite a good price too, and you get a lot of extras over the 6680 - does anyone know if Timelab will work with a 6681? Angus. On Sun, 15 Nov 2015 15:10:42 -0800, you wrote: >Thanks Bob > >I'm using the actual time pod for paying activities. This would be a counter >for time nuttery using the time pod software. In those cases Where I don't >want to fire up the 5071. > >I'm familiar with the Keysight counters and I have a lot of them into the high >Ghz ranges > >The 53131 is spec'd to 500ps and the 6680 is spec'd at 250ps > >I've also been leaning in the 53131 direction but I'd like to have the best >tool for the job at hand > >Content by Scott >Typos by Siri > >> On Nov 15, 2015, at 1:59 PM, Bob Camp <kb...@n1k.org> wrote: >> >> Hi >> >> I guess the first question would be - If you have a Time Pod, what do you >> need a counter for? >> >> Based on a guess that you need extended frequency range, either would do >> pretty well. My vote >> would go to the HP for a couple of reasons: >> >> 1) Its more broadly supported in terms of driver software (which may or may >> not matter to you). >> >> 2) Its a more common item on the auction sites, so parts are easier to find. >> >> 3) It shares some parts (like the power supply) with the (cheaper) 53181 >> >> No those are not great big reasons to go for one over the other. They are >> very similar devices. One >> has an LCD that has a finite life. The other has a VFD that also has a >> finite life. Both are custom, thats >> a tie. Some like the command (button) arrangement on one over the other. I >> think its more a what >> are you used to thing than anything else. On the 53131 you need to hit the >> Run button in some cases. >> >> I have not watched the prices on the Fluke. I have kept track of the >> 53131s. A good price on one >> these days is below $600 ( = you may need to shop a bit, but they do show >> up). >> >> Bob >> >>> On Nov 15, 2015, at 1:45 PM, Scott McGrath <scmcgr...@gmail.com> wrote: >>> >>> Hi >>> >>> Which counter would be best for use with time pod I have a chance to buy >>> each at a reasonable prices i.e. < 1000 US >>> >>> Thanks in advance Scott >>> >>> Content by Scott >>> Typos by Siri >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Trimble GPS board
On Sun, 23 Aug 2015 23:36:27 -0400, you wrote: Hi Angus, Thanks for your reply. My original suspicion is the +6.5V rail. That needs to come from somewhere, and you need headroom if it's an unregulated input. Pumping 2A through a regulator like that is no easy feat. Although rated for 3A, you need to keep the junction temperature below 125C. The part has a 30C/W thermal resistance (Tja) with a 1 square copper pad. So 6.5V and 3A calculate as follows: (6.5V-5V)*3A=4.5W. 4.5W*30C/W=135C RISE, add that to ambient, 25C, and you are 35C over max junction. In my world we have a 70C ambient, and that leaves me (125C-70C)/30C/W=1.83W, or a maximum of 1.83W/1.5V=1.22A. Generally a tab mounted TO-220 (a D2Pak) can have a Tjc (junction to case) or less than 1C/W. It's all the reest of the mounting that piles on the thermal resistance. The Trimble board has a top layer pad, some far side pad, and probably multiple layer of ground plane over the rest of the board. The mounting post is mostly likely part of the thermal resistance calculation. There is also a time constant involved, it probably can't take the 2A forever, just long enough to get the oven up to temp. I suspect they may have gotten the thermal impedance down as low as 10C/W. I will test it with 12V and let everyone know if I fry the board. Bob Hi Bob, There's not really any need for a 6V or so rail - a DC-DC converter (and probably some filtering) can provide the right voltage just where it's needed. What looks like a Symmetricom variant is in listing #271483752431. It does appear to have a DC-DC converter, etc., on the board. Anyway, I dug out my Trimble to have a look at it, and I see that there's a 10V tantalum capacitor on the input power, so it's certainly not meant to run on 12V. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Trimble GPS board
On Sat, 22 Aug 2015 18:25:04 -0400, you wrote: rbenward at verizon.net wrote: See below, here is a 73090 OCXO (same as on some of those GPSDO boards) powered by +12V. You are incorrect in your assumption that the link you have supplied shows a 73090 OCXO powered by +12VDC. The BOARD is indeed powered by 12VDC (or 15VDC if you read the listing) but if you look at all the photos you will see a 3-terminal regulator on the bottom of the pc board. Hi, It does indeed have a reg, but as far as I can see it's a 7812 that's in the picture in the listing. This would also explain why it has a 12V or 15V selector link. I'm not suggesting that it's a 12V osc - on my 57963-80 it is definitely fed just 5V from the regulator. I also used 6V for the power supply. It also appears just to be a basic, fast warm-up AT OCXO, which fits in with the short time constant on the GPS control loop. Angus. The Trimble GPSDO I'm supplying 6.3VDC to had a 5 volt regulator that has a measured output of 5.00VDC and the supply pin on the oscillator had that 5.00VDC on it, not the 6.3VDC from my supply. A continuity check shows a direct connection from the regulator's 5 volt output directly to the oscillator's supply pin. Because of the higher current drawn by the 5 volt oven, running the input to the board at 12VDC and wasting all that power as heat would not be wise. 6.3VDC makes me happy and they chose a LDO regulator for a good reason. The one error I did notice is I said the board locked after it found satellites but that is incorrect. It does find satellites quickly but takes about 10 minutes to lock and that is when the 10Mhz output is enabled. I did some of my checking around 1AM and that is not a good time for clear thinking or writing. -Arthur ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Trimble GPS board
Hi Bob, I got a Trimble 57963-80 last year and the 73090 OXCO and some other parts on it are supplied with 5V from the LT1764A. The DSP, FPGA, etc., also have various small regulators supplying their supply voltages - one even has a dropper resistor in series. These are connected to the main input supply, so raising it above what it should be is probably not a good idea. I thought at first that the LT1764A would be thermally connected to the fixing hole beside it so that the heat could be removed, but it is only connected to the copper on the top of board at that point - then again, that may be the way it was mounted. I did put a temp sensor on the 1764 to see how much it heated up during warm up and when running, but neither looked close to being a problem when run at 6V and room temperature. At 6V, it took 2A during warm up and just over 1A when running at room temp, but the warm up is fast. When I got the board, someone had written on the OCXO with a marker pen what the pins were, and the power was marked as 12V, and an EFC voltage was also written on (about 0.2V from what I measured) which was all a little weird. It was listed as having been tested, but since the seller said that they had no connection info, who tested it and how is anyone's guess... Angus. On Sat, 22 Aug 2015 14:02:35 -0400, you wrote: Hi Arthur, Thank you for this information. I have not received my board yet, I probably still have a few weeks to go. The LT1764 will take up to 20V, but I would never go to the edge. You could easily do 12V, the only downside is the dissipation in the LT17654. Use a variable power supply and raise the voltage slowly. Monitor the temperature with a thermocouple, IR spot meter (radio shack had one for $10), or just use your finger. If you can keep your finger on it comfortable for a long period of time, the temp should be OK. The junction temp is rated for 125C. Now on the flips side, my only concern is the regulator is not supplying the oven power. Most Trimble OCXOs I see on Ebay are powered by +12. When supplying only 6.5V the oven might not get up to temp producing frequency instability and some erratic EFC stats. See below, here is a 73090 OCXO (same as on some of those GPSDO boards) powered by +12V. It's possible the regulator is meant to be powered from +12V, supplying power to the digital logic and to the oscillator portion of the OCXO. Then +12V directly supplies the oven. http://www.ebay.com/itm/10-00MHz-Trimble-Double-Oven-OCXO-Trimble-73090-Double-sinewave-15V-12V-/251883335405?hash=item3aa56aaeed I will post my success and let everyone know how I make out. I purchased this to have a backup for my Z3801 Z3805. Both are on the fritz, I will be post those trials and tribulations on a new thread. Thanks so much for your response. Bob ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Trimble GPS board
On the left front corner of the board is the 1 PPS connector. To the right of that connector are 4 unpopulated holes for a connector. I traced those out and found 2 went to a RS-232 chip that appears to be a different type depending on which of the boards you receive. The left hole is ground (RS-232 pin 5 on the computer end), then the next hole is not connected, then RS-232 pin 2, then pin 3 being the hole with the square index pad on the right. Using a terminal emulator program and 57600 8N1N I was able to communicate with the board. Typing '?' will give you a long list of all the commands it will accept. For instance, 'STAT' and 'POSSTAT' are 2 of the commands that will give you info on how the board is working. Typing *IDN? at the UCCM-P prompt returns 57964-60 for my board and POSSTAT shows up to 12 satellites can be tracked. The date code on my unit is 2009. The board seems to work well but the OCXO runs pretty hot so it probably isn't a double oven. The multicontact connector probably has most of the functions and LED signals available but I couldn't see using it so I'll get whatever signals I want directly off the pc board. Hi Arthur, That's interesting - I connected my one up to Trimble studio and others, but got no joy - I never thought of just asking it :) I went through the connections on the other pins, but most are just to the FPGA or 0V. Most don't appear to be doing a lot - maybe they need whatever is meant to be connected to this board to be connected before they do anything. There is another serial port which is the same baud rate but appears to be binary, and prattles away every 2 seconds: Pin 36 goes to Pin 4 of the UART (RX) Pin 37 goes to Pin 8 of the UART (TX) Pin 2 has binary data of about 64 bits at 1.6us/bit - looks like maybe a timer or similar. (Above pin numbers assume V+ is connected to pins 44-50 and are hopefully correct, but always worth checking) Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] new tdc from Texas
Oops, I wasn't paying attention when I looked at the GP30 info - like Maxim, Acam has gone down the 'more integration' route and buried the actual TDC under a heap of other stuff, which does rather limit its usefulness. (data sheets have appeared for it now) Oh well, nice idea while it lasted. Angus. On Thu, 05 Mar 2015 01:27:23 +, you wrote: Hi, I've not seen any mention of anything other than the TDC1000. I was a bit surprised that they went down the less-integrated route and separated the TDC, but it turns out that for a lot of the sort of things they designed it for, a uC provides good enough timing itself, and no extra TDC is needed at all. I see that Acam have released a bit more info on their new GP30, although no data sheet yet. It quotes typical LSB of 11ps, and rms noise of 1.2 LSB, which is quite an improvement on the GP22. It would just be good if they offered a simple online way of getting low volumes of them - I suspect that the specialist distributors would be just as happy as the customers would be! Angus. On Tue, 03 Mar 2015 15:43:25 -0800, you wrote: Hi Angus: Do you know if they have an IR pulse front end which would be more interesting than the ultrasonic front end? Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Angus wrote: In case anyone is interested, the full data sheet is on the TI site now, although I didn't see any actual IC's yet other than the ones in the eval boards. Angus. On Tue, 17 Feb 2015 21:24:08 -0200, you wrote: Initial datasheet: http://www.ti.com/lit/ds/symlink/tdc7200.pdf EVM: http://www.ti.com/tool/tdc1000-tdc7200evm Seems good... what do you think? Daniel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] new tdc from Texas
Hi, I've not seen any mention of anything other than the TDC1000. I was a bit surprised that they went down the less-integrated route and separated the TDC, but it turns out that for a lot of the sort of things they designed it for, a uC provides good enough timing itself, and no extra TDC is needed at all. I see that Acam have released a bit more info on their new GP30, although no data sheet yet. It quotes typical LSB of 11ps, and rms noise of 1.2 LSB, which is quite an improvement on the GP22. It would just be good if they offered a simple online way of getting low volumes of them - I suspect that the specialist distributors would be just as happy as the customers would be! Angus. On Tue, 03 Mar 2015 15:43:25 -0800, you wrote: Hi Angus: Do you know if they have an IR pulse front end which would be more interesting than the ultrasonic front end? Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Angus wrote: In case anyone is interested, the full data sheet is on the TI site now, although I didn't see any actual IC's yet other than the ones in the eval boards. Angus. On Tue, 17 Feb 2015 21:24:08 -0200, you wrote: Initial datasheet: http://www.ti.com/lit/ds/symlink/tdc7200.pdf EVM: http://www.ti.com/tool/tdc1000-tdc7200evm Seems good... what do you think? Daniel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] new tdc from Texas
In case anyone is interested, the full data sheet is on the TI site now, although I didn't see any actual IC's yet other than the ones in the eval boards. Angus. On Tue, 17 Feb 2015 21:24:08 -0200, you wrote: Initial datasheet: http://www.ti.com/lit/ds/symlink/tdc7200.pdf EVM: http://www.ti.com/tool/tdc1000-tdc7200evm Seems good... what do you think? Daniel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Removing FTS 1200/1000A ovens.
Hi, Can anyone tell me if there is a particular method for removing the oven from the flask in a FTS 1200 or 1000A - it seems pretty well wedged in there. Thanks, Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS position averaging
On Mon, 15 Dec 2014 17:55:20 -0500, you wrote: Hi Simple answer - there is no simple answer. You will get significantly better results by intelligently processing the data than by a giant average everything in sight approach. Also consider that various GPS modules seem to have offsets in their nav solution. The NIST papers on various GPSDOs show this pretty clearly. Simply having a correct solution may not help as much as you might think. Of course if you want a truly correct solution, your local surveyor is indeed your best friend. He probably has a GPS gizmo that with about a half hour or sitting there, tell you where you are to under an inch. Who knows how much that will cost. It probably depends on how interested you can get him in coming over and looking at your toys. But is it the closest to the 'true' position that you really want, or the best estimate of where the particular GPS you are testing thinks it is? Angus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Linear voltage regulator hints...
Hi Dan, Have you varied the of the GPSDO board itself, say by covering it, shining a lamp on it, blowing a fan on it, or something? (It would be even better if you could vary the temperature of parts of it separately) If you're seeing supply voltage variations, you could then just vary the supply and see what happens. You may have done this already, but I just didn't see it mentioned. Angus. On Thu, 11 Dec 2014 07:13:14 -0500, you wrote: Yeah, I suffer from time-nuts digest lag, family lag, day job lag, among other things. So please excuse delayed responses... The oscillator has proven to be relatively immune to 'reasonable' changes in voltage, as would be expected. About the range of Numbers Bob Camp has suggested, or maybe even better. The EFC voltage is not an issue at this point. It was previously, and the solution to that was a low drift 'roll your own' design. It would be nice to replace it with a COTS part, but it looks like there aren't any available. Thus the reason for pinging the list. Sometimes you all pull things out of thin air... ;) That said, the LT3081 looks interesting. At the very least it's easily controllable from an external source. I've got a few on order, and if it pans out I'll report back here. What I'm after right now is in reality small. Temp cycles are somewhat apparent from looking at what the EFC voltage is doing locked with the GPSDO. It's on the order 10^-12 range, if I did my math right. It is visible, so it may be worth trying to fix. Of course, now that Bob has his new CS to play with anything I do is judged by a completely different standard! ;) Again, thanks for the responses! Dan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Did a member of time-nuts buy this?
On Sun, 7 Dec 2014 19:34:02 -0500, you wrote: Hi On Dec 7, 2014, at 7:15 PM, Angus not.ag...@btinternet.com wrote: On Sat, 6 Dec 2014 11:47:10 -0500, you wrote: I am looking forward to long term data on the Lucent unit. GPSDO's are getting closer and closer to Cesium. Having worked for 18 month on two GPSDO projects we find that the limiting factors are the Cesium Standards. Working presently on a Cesium GPSDO. Short term OCXO, medium Rb and long term Cesium. With Cesium may be able to use 14 day filter. Will find out. If we do not see an improvement we will most likely retire our Cesium units. Bert Kehren Hi Bert, Out of curiosity, what Rb are you using, and how does it respond to air pressure changes? Properly identifying / measuring pressure induced drift is not as easy as one might think. The tweak and see approach seems to be the best bet. Hmm I wonder who originally suggested that . oh, yea it was Angus. That depends a lot on the Rb. With a temperature controlled LPRO it's easy - just logging air pressure against frequency get you most of the way. With the LPRO's I've tested that gets the variation with pressure to down under +/- 2E-13, some well under, over 60mbars pressure range. I have one that had almost no residual left after correction, though the others had a little. Getting past that is harder. There is also some time lag - looked like something around 3/4Hr, but with GPS as my reference and air pressure moving so slowly, it was hard to tell. Of course the lower the numbers, the more error sources start to become significant, but since the LPRO's I've test are all around 8E-14/mbar, it's not exactly hard to measure. It is time consuming though, since it normally took 3-6 weeks to do each test, depending on the weather. Interestingly, the both the FE5680A's I tested had similar responses to pressure variations - very variable compared to the LPRO's, so impossible to correct simply and well. Seeing the comments about the temp correction in FE5680A's causing problems, I did wonder if that might be part of the problem, but have not got around to testing that yet. Angus. Bob Combining temp control, air pressure compensation and drift compensation can give very good results with the right Rb. Angus. In a message dated 12/6/2014 10:46:57 A.M. Eastern Standard Time, kb...@n1k.org writes: Hi On Dec 6, 2014, at 10:35 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Bob, On 12/06/2014 04:16 PM, Bob Camp wrote: Hi On Dec 6, 2014, at 9:54 AM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I see this cesium reference on eBay, where apparently someone returned it due to the fact it had a bad tube. http://www.ebay.com/itm/HP-Agilent-5061A-Cesium-Beam-Frequency-Standard-FOR-PARTS-REPAIR-/141483787108 I'm wondering if it was someone on this list. It is likely to be practical to replace the tube? New tubes for Cs standards are in the $20K range. Getting a modern one re-tubed with a high performance tube is $32K. The stock of ?new old stock? tubes is long gone. About the only tubes you see are pulls from used gear. The question with them (as with any Cs) is just how many years (or months) is left on the tube. You physically move Cs from one end of the tube to the other when you operate the device. One you have exhausted the pre-loaded stock, the tube is dead. It?s also coated all over the inside with surplus Cs. Since signal to noise ratio is very important, the drop in Cs at end of life and crud on the inside leads to degradation in the performance towards the end of the tube life. Even if the tube works, it may (or may not) be useful in a given application. For many applications, GPSDO?s are the more useful device. Their performance rivals that of most of the older Cs standards. They are way cheaper, and they don?t wear out. Indeed, if you have a 5071A with a high performance tube in it, a GPSDO is not going to match it?s performance. I?ve replaced two tubes in one of those, so they are correct when they talk about the projected life of the tube. The other subtle issue with Cs standards is shipping. If you are going to do it ?right? it?s a major pain. Sending one back for re-tube does require you to do all the formal shipping nuttiness. That may or may not be an issue on the surplus market . Well, there is one use-case for a cesium, which is the validation of GPS receivers. Rubidiums do help to some degree. Comparing two GPS clocks with their highly systematic sources, so you can't get useful differences that way for the stability of the produced signal. Unless you are making a GPS receiver from scratch (which you might be), there is a certain ?trust factor? that comes into using a GPS for timing. Since you can?t play with the firmware, you trust that the guy
Re: [time-nuts] TIC users
On Sat, 6 Dec 2014 16:44:40 -0700, you wrote: Ran across this in my 'net travels: http://www.maximintegrated.com/en/products/analog/sensors-and-sensor-interface/MAX35103.html American supplier, 20 ps accuracy claimed time interval to digital. Don That's an interesting chip - I've not come across it before. The TDC in it appears good, although there are limited details given on it. From the data sheet, the main complication looks to be that its hardware and software are so optimised for use as a low power flow meter that any more general use is very restricted. It does not seem to allow the simple time interval measurements that the Acams or THS788 do. Now if only they did a pure TIC version - but that might be a little optimistic since Acam also seem to be really pushing the flow meter side. That must be where the volume is... Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Did a member of time-nuts buy this?
On Sat, 6 Dec 2014 11:47:10 -0500, you wrote: I am looking forward to long term data on the Lucent unit. GPSDO's are getting closer and closer to Cesium. Having worked for 18 month on two GPSDO projects we find that the limiting factors are the Cesium Standards. Working presently on a Cesium GPSDO. Short term OCXO, medium Rb and long term Cesium. With Cesium may be able to use 14 day filter. Will find out. If we do not see an improvement we will most likely retire our Cesium units. Bert Kehren Hi Bert, Out of curiosity, what Rb are you using, and how does it respond to air pressure changes? Combining temp control, air pressure compensation and drift compensation can give very good results with the right Rb. Angus. In a message dated 12/6/2014 10:46:57 A.M. Eastern Standard Time, kb...@n1k.org writes: Hi On Dec 6, 2014, at 10:35 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Bob, On 12/06/2014 04:16 PM, Bob Camp wrote: Hi On Dec 6, 2014, at 9:54 AM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: I see this cesium reference on eBay, where apparently someone returned it due to the fact it had a bad tube. http://www.ebay.com/itm/HP-Agilent-5061A-Cesium-Beam-Frequency-Standard-FOR-PARTS-REPAIR-/141483787108 I'm wondering if it was someone on this list. It is likely to be practical to replace the tube? New tubes for Cs standards are in the $20K range. Getting a modern one re-tubed with a high performance tube is $32K. The stock of new old stock tubes is long gone. About the only tubes you see are pulls from used gear. The question with them (as with any Cs) is just how many years (or months) is left on the tube. You physically move Cs from one end of the tube to the other when you operate the device. One you have exhausted the pre-loaded stock, the tube is dead. Its also coated all over the inside with surplus Cs. Since signal to noise ratio is very important, the drop in Cs at end of life and crud on the inside leads to degradation in the performance towards the end of the tube life. Even if the tube works, it may (or may not) be useful in a given application. For many applications, GPSDOs are the more useful device. Their performance rivals that of most of the older Cs standards. They are way cheaper, and they dont wear out. Indeed, if you have a 5071A with a high performance tube in it, a GPSDO is not going to match its performance. Ive replaced two tubes in one of those, so they are correct when they talk about the projected life of the tube. The other subtle issue with Cs standards is shipping. If you are going to do it right its a major pain. Sending one back for re-tube does require you to do all the formal shipping nuttiness. That may or may not be an issue on the surplus market . Well, there is one use-case for a cesium, which is the validation of GPS receivers. Rubidiums do help to some degree. Comparing two GPS clocks with their highly systematic sources, so you can't get useful differences that way for the stability of the produced signal. Unless you are making a GPS receiver from scratch (which you might be), there is a certain trust factor that comes into using a GPS for timing. Since you cant play with the firmware, you trust that the guy who wrote it did a good job. In making a GPSDO, yes on a commercial basis verification against primary standards is likely to be required by this or that customer. In a basement lab, Im not so sure thats true. Simply comparing things against an ensemble of known good designs (and cross checking the results) should be good enough. If your design passes the performance of the ensemble, building several of your design is likely to be cheaper than keeping a Cs running long term. Thats even more true if you need a fully functional 5071A to do the comparison. Lets see .. new BMW or rebuild the 5071 hmmm :) Bob Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] tcxo
On Sun, 7 Dec 2014 21:53:48 +0100, you wrote: Something that keeps a constant temperature that is that I can then glue/solder to the crystal of those systems. A ready to go version (QH40A): http://shop.kuhne-electronic.de/kuhne/en/shop/amateur-radio/accessoires/crystal-heater/Precision+crystal+heater+40%C2%B0+QH40A/?card=724 Angus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Homebrew frequency counter, need help
On Thu, 27 Nov 2014 08:20:59 -0800, you wrote: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. Just happened to notice that there are actually a few breakout and development boards on aliexpress based on the TDC-GP21, which is very similar to the GP22. Nothing as impressive as a complete frequency counter of course, but might be a quick and painless way to start playing with the chip. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Homebrew frequency counter, need help
On Fri, 28 Nov 2014 21:04:27 +0800, you wrote: The TDC-GP22 is the best choise for me at the moment. Since I am not a hardware guy, simplicity is important. It's very cheap in China(About 3$ for each piece ). TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us between stop channels). Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and 22ps in quard_res mode(1 stop only) The biggest problem I met: If you trigger start first, 100ns later stop1, another 100ns later stop2.Get the result of stop1-start and stop2-stop1. You will find stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% level ). Dont know if it's my problem or theirs. Here is the configuration of it (the document is very bad, took me 3 weeks to play with these 6 registers to get it work as I expected) and schematic. Register_0 = 0x00c42700, Register_1 = 0x19498000, Register_2 = 0xe000, Register_3 = 0x, Register_4 = 0x2000, Register_5 = 0x1000, Register_6 = 0; Hi, That's very interesting. I've been planning to do a basic board with a GP22 for a while - something like the acam evaluation board but with some input circuitry, and plugged into a fast microcontroller board. Could not decide what one, so I thought that an arduino-type board would be the most flexible for now. I mainly just want to test it until it squeaks. Now that winter is coming and I've got all the bits, I'll hopefully get time to do it. First job is QFN soldering. That should be fun I thought it looked like setting up the registers could be a bit of a problem. The manual for the evaluation kit says that there are some example setups included - I did wonder if it might be possible to see that and other info if the software was installed and run, even without their board connected, but did not try that yet. Angus. 2014-11-28 0:20 GMT+08:00 Tom Van Baak t...@leapsecond.com: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Homebrew frequency counter, need help
On Fri, 28 Nov 2014 08:57:37 -0600, you wrote: Hi On Nov 28, 2014, at 7:04 AM, Li Ang lll...@gmail.com wrote: The TDC-GP22 is the best choise for me at the moment. Since I am not a hardware guy, simplicity is important. It's very cheap in China(About 3$ for each piece ). Which is a very good reason to play with it TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us between stop channels). Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and 22ps in quard_res mode(1 stop only) All of which is *plenty* good enough to make a decent counter. That assumes that they are talking about accuracy (even 1 sigma) rather than just the resolution of the LSB. Specs are often confusing on parts like this. Hi , Unfortunately the 22ps etc is just resolution and there is also a fair bit of noise - some typical SD's are given in the data sheet which vary from 35 to 72 ps depending on the settings, and that only covers part of the range. 60ps RMS noise is also mentioned. The nominal clock input is 2-8MHz, but the 22ps range is only available for clocks 6MHz, and not in Mode1 which is being used. Should still be enough to give most counters a workout. Angus. The biggest problem I met: If you trigger start first, 100ns later stop1, another 100ns later stop2.Get the result of stop1-start and stop2-stop1. You will find stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% level ). Dont know if it's my problem or theirs. This may be the resolution / accuracy thing I mentioned above. Dont give up quite yet though. Here is the configuration of it (the document is very bad, took me 3 weeks to play with these 6 registers to get it work as I expected) and schematic. Gee that sounds like the documentation on a LOT of parts these days . Its also what keeps people from trying this sort of thing. A few hardware questions: 1) What frequency is the crystal at? (can you drive the chip from an OCXO?) 2) Is there more bypassing on the circuit than shown? (If not, add some more). 3) How confident are you of your input signal? (can you check it with a known good counter?) 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it may not be helping things ) A full counter will have a bit more stuff than just this chip. I think getting this part working *before* you work on the rest of it is a very good idea. One small piece at a time . Bob Register_0 = 0x00c42700, Register_1 = 0x19498000, Register_2 = 0xe000, Register_3 = 0x, Register_4 = 0x2000, Register_5 = 0x1000, Register_6 = 0; ? 2014-11-28 0:20 GMT+08:00 Tom Van Baak t...@leapsecond.com: Your project sounds wonderful. The TDC-GP22 has been mentioned only a few times over the years and I keep waiting for someone to post actual results from this chip, or better yet -- schematics, photos, and source code. tdc_gp22.GIF___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 10MHz Rubidium reference source for frequency counter
On Sun, 2 Nov 2014 12:13:34 +0300, you wrote: Mode has been switch from Frequency to TI - result is much better now. It was the main improvement in my measurement. Thanks a lot! Picture of ADEV OCXO result - https://dl.dropboxusercontent.com/u/21338179/hamradio/OCXO_Adev/OCXO%20ADEV%20TI%20mode%2020141102.jpg Hi Karen, You appear just to be measuring the ADEV of your counter in single shot TI mode here, not the oscillators - how exactly do you have the counter and oscillators connected up? If I was doing it I'd probably try start by setting the counter to measure freq in Smart Freq mode, and set it to ext ref, with one morion feeding the external reference and another on the input. If the morions are ok you should get towards 1E-11 at 1 sec (if I'm reading the specs correctly) If not, try other oscillators and see if anything changes. As John said, TI is more complex to do anyway, and with quartz that has not had days or even weeks to settle it's a total pain. Angus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 10MHz Rubidium reference source for frequency counter
On Fri, 31 Oct 2014 23:40:04 -0400, you wrote: John wrote: It seems to me that it's just a case of expecting too much from a counter. Possibly, but a well-tuned 5370B can get to the low e-12's at 1-10 seconds. It has better one-shot resolution than the Pendulum, but not by a factor of 10. So, I'd have thought the Pendulum would at least get to the mid e-11's if the time base was up to it. The 'Smart Freq' feature on the CNT-91 appears to do multiple measurements over the gate time to get an improved resolution, kind of like the 53131/2. In practice, when 11 digits or whatever are claimed, I usually find that there is just a little bit of information in the last digit, not that it's a solid reading to that number of digits. In the Measurement Uncertainties section of the manual, would the formula for frequency suggest that Smart Freq makes the result up from multiple measurements of 0.4 times the nominal gate time? To get the best performance from a counter, you need to set up the trigger thresholds well away from ground as Charles says. Also consider taking TI readings rather than frequency readings. Frequency readings are OK for initial setup and basic ADEV comparisons but they won't generally yield the best ADEV fidelity or the lowest possible measurement floor. Yes, using TI mode is essential for getting down to the counter's limits. Was Karen using frequency mode? I wasn't paying attention to that end of things. I don't know exactly how the CNT-91 does it, but the older CNT-81 can do a lot of measurements in Time Interval A to B mode. With a static delay, my 6681 gives a SD of about 0.22ps for a set of 100 1-second measurements (a 10MHz square wave was driving the inputs). One little thing I noticed there was that the reference freq needed to be at least 3ppm off the input frequency to get quite that low. The newer series seem to need a bit of an offset too: https://www.febo.com/pipermail/time-nuts/2014-September/086701.html Angus. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some specs for MTI Millren 260 OXCOs
Google Scholar finds 2 links under the original name too - it can be quite good for finding free copies easily. Angus. On Thu, 23 Oct 2014 17:30:22 -0400, you wrote: More than one way to skin an egg, or something like that anyway:-) A Google search on Vaish Milliren turned up this paper and another on the 260. _www.mti-milliren.com/MTIPapers/Rubidium_Perf_in_260.pdf_ (http://www.mti-milliren.com/MTIPapers/Rubidium_Perf_in_260.pdf) _www.mti-milliren.com/MTIPapers/High_Vol_Production.pdf_ (http://www.mti-milliren.com/MTIPapers/High_Vol_Production.pdf) The site wouldn't allow access just into the MTIPapers directory but the full URLs seem to work ok Regards Nigel GM8PZR In a message dated 23/10/2014 22:12:17 GMT Daylight Time, p...@petelancashire.com writes: Anyone have a IEEE account ? http://ieeexplore.ieee.org/xpl/login.jsp?tp=arnumber=560251url=http%3A%2F% 2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D560251 -pete On Thu, Oct 23, 2014 at 1:07 AM, Hal Murray hmur...@megapathdsl.net wrote: dgmin...@mediacombb.net said: The model 260 datasheet is on MTI's web site at http://www.mti-milliren.com That data sheet covers their standard models. You can see the part number in the far right column of the table on the bottom of the last page of the double page spread. They are likely to have a few in stock. They also make lots of specials. Tell them the specifications you want and they will make a new part number, put it into their system so you can easily order it, and keep the details private so your competitors have more work to do if they want to clone or reverse engineer your designs. If the part number on a unit you get from eBay isn't on the data sheet, it's probably a special. You can get a general idea from the data sheet but you will probably have to measure it if you want the fine print. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DIY FE-5680A lobotomy (disable temp compensation)
On Fri, 04 Jul 2014 02:35:41 +0100, you wrote: Hi Bert, I am thinking about testing a heat pipe on a fan cooled setup I use. The first temp controlled chassis I did used a peltier and works very well, but was a lot more work to do and is much more power hungry. The main problem I find is not the temp controller itself, but rather the change in the temperature across the chassis as the ambient changes. However good the temp controller is, it only controls a single point, but other points further away from the sensing thermistor can vary a lot. I noticed you posted a picture of a heat pipe cooler a couple of weeks ago - did you happen to compare the temperature across the unit with direct fan cooling and the heat pipe cooler, or with different heat pipes? Angus. I finally got around to playing with a couple of laptop heat pipes, fixed to a 25x50x75mm block of aluminium which is fixed to the 12mm thick baseplate. On a quick test of it, a sensor near the end of the baseplate showed 1.5-2x greater variation with temperature compared with just having a fan blow directly onto the baseplate. The oscillator also had to be allowed to run a few degrees C hotter for the heatpipe coolers to work to the same max ambient temp. One cooler had two heatpipes with about 12cm between the aluminium block and the heatsink fins (cast in this case) The other had a single, wider heat pipe with about 5cm between the block and the heatsink (this time with a lot more fine fins) The second cooler was rather more efficient, allowing a extra degreee of cooling at the top end, but more problematic was that it entered 'bang-bang' mode with the analogue temperature controller even sooner, and the temperature fluctuations there were greater. Both were rather worse than with the fan just blowing onto the baseplate. Using a PWM fan controller would help a good bit, but getting more creative with a microcontroller would be better. That way you can give the fan a minimum of a small kick every so often, and vary the repetition rate as well as the duty cycle as more cooling is needed. With feedback from the fan and even air temperature monitoring, you could get a good idea of exactly how much cooling was being applied. Another problem is that the overall temp control range is lower with the coolers - barely 8-9 DegC compared with 12+ DegC with the fan blowing directly on the baseplate. That's mainly the result of the poorer cooling at the top end of the range. The Rb osc fitted during this test was a SA.22c which takes a good bit less power than a 5680A, and the fan blowing onto the baseplate was normally a 60mm one fitted about 50mm away from it. The baseplate was horizontal with the fan blowing onto it from below. Maybe fitting a heatsink directly onto the base would help further with the maximum temp, but it would increase the convection cooling at the minimum temp, reducing the overall benefit. It could also be more susceptible to drafts, and would make the fan control much more delicate. Anyway, that's the results I got with my setup. Other setups and more fine tuning could change things a good bit, but I just wanted to get an idea of how the two cooling methods compared on the same setup. Angus On Sat, 28 Jun 2014 12:37:37 -0400 (EDT), you wrote: Will someone beside us use heat pipe. Would love to have an impendent input. What does it take to get a test going. Scott has done a lot of work, how about some one else step up to the plate. There are a lot of time nuts out there with the 5680A,many for the first time will have a very good reference and some of our experts with proper equipment can make a big difference. Bert Kehren In a message dated 6/28/2014 12:20:12 P.M. Eastern Daylight Time, newell+timen...@n5tnl.com writes: At 04:32 AM 6/28/2014, wb6bnq wrote: monitoring process ? In other words have you traced out the connections to see what is driving the pin you think is the temperature input ? No. I've only traced back from the ADC input to the voltage divider. The next big question is have you monitored the frequency and its stability, externally, to observe what effects are taking place when you disable this input to the A/D ? I have not. That sounds complicated and messy but may be easier than it appears. An appropriate container would be: It does sound messy. I don't think I'm willing to dunk one of my units. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DIY FE-5680A lobotomy (disable temp compensation)
Hi Bert, I am thinking about testing a heat pipe on a fan cooled setup I use. The first temp controlled chassis I did used a peltier and works very well, but was a lot more work to do and is much more power hungry. The main problem I find is not the temp controller itself, but rather the change in the temperature across the chassis as the ambient changes. However good the temp controller is, it only controls a single point, but other points further away from the sensing thermistor can vary a lot. I noticed you posted a picture of a heat pipe cooler a couple of weeks ago - did you happen to compare the temperature across the unit with direct fan cooling and the heat pipe cooler, or with different heat pipes? Angus. On Sat, 28 Jun 2014 12:37:37 -0400 (EDT), you wrote: Will someone beside us use heat pipe. Would love to have an impendent input. What does it take to get a test going. Scott has done a lot of work, how about some one else step up to the plate. There are a lot of time nuts out there with the 5680A,many for the first time will have a very good reference and some of our experts with proper equipment can make a big difference. Bert Kehren In a message dated 6/28/2014 12:20:12 P.M. Eastern Daylight Time, newell+timen...@n5tnl.com writes: At 04:32 AM 6/28/2014, wb6bnq wrote: monitoring process ? In other words have you traced out the connections to see what is driving the pin you think is the temperature input ? No. I've only traced back from the ADC input to the voltage divider. The next big question is have you monitored the frequency and its stability, externally, to observe what effects are taking place when you disable this input to the A/D ? I have not. That sounds complicated and messy but may be easier than it appears. An appropriate container would be: It does sound messy. I don't think I'm willing to dunk one of my units. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Trimble 57963 PCB (GPSDO?)
Hi, I noticed these while wasting yet more time on ebay, and was wondering if anyone knows anything about them. Trimble 57963-80-D PCB #301124758583 I'm assuming that it's a GPSDO board that the oscillator is sitting on. Thanks, Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Acam TDC's
Hi, It's not exactly cutting edge resolution etc, but for a ready to go chip, it's not at all bad. In theory, it looks like it should be useful in a lot of the places that counters like a 53131/2 get used, but it can sample very much faster than them. It also has useful temperature inputs. Most of the projects I've come across don't stretch its performance so I'm just interested if someone has really tested it. If not, I expect I'll find out more when I get it up and running. Angus. On Fri, 4 Apr 2014 18:27:05 -0400, you wrote: Angus An interesting chip. I had never heard of it before and suspect this may be the gizmo used in closed system water leak detection. Won't go into why I know about that. I did find comments from 2007 about the chip and atmega but nothing since. When I went looking for distributors or pricing to get an idea came up empty. Though Amazon will sell you lots of vitamins or something called TDC. So with all that said I will guess that for time-nuts purposes the capabilities of this chip have been far exceeded by the various array technologies we have at very cheap prices today. The ability to create long counters at very high speeds. Only a guess though. Regards Paul. WB8TSL On Fri, Apr 4, 2014 at 5:35 PM, Angus not.ag...@btinternet.com wrote: Hi, With all the recent talk of interpolators, I started looking at the acam TDC chips again - the GP22 is pretty cheap now for anyone who's up for playing with the tiny QFN package. I was wondering if anyone here has tried them or properly evaluated them as a TIC - especially the GP2/GP21/GP22. A few years back a some folk were talking about it, but I did not hear much since that. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Acam TDC's
Hi, With all the recent talk of interpolators, I started looking at the acam TDC chips again - the GP22 is pretty cheap now for anyone who's up for playing with the tiny QFN package. I was wondering if anyone here has tried them or properly evaluated them as a TIC - especially the GP2/GP21/GP22. A few years back a some folk were talking about it, but I did not hear much since that. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The 5MHz Sweet Spot
Yes, but as with quartz it varies a lot. I have tested a few LPROs, but have never seen a frequency jump in them. Those with more to test might have seen some jumps, but mine have been well behaved whenever they were being logged anyway. I don't remember seeing actual jumps in the FE5680A's either, although the 2 older style 1pps-only ones did often have retrace jumps (like 5-10ppt) even after a short power down. The most obvious jumps I have seem were on a Temex LPRO/LPFRS which also had a borderline low peak Rb voltage, whether that had anything to do with it or not. At first it sometimes jumped in steps of 5-20ppt, and tapping it or even touching the connector on the RF cable from it would also often cause a jump. It was at its worst when I first powered it up, but even after many weeks on, they were still there occasionally. I've also tried a couple of the 9.8304MHz Sa.22c things recently, and other than being very basic spec, one had some fast frequency jumps and the other none that I saw - although near the middle of a 7 week test run it decided to change by 3E-11 over 15 hours or so. That is actually very like what I've seen sometimes in quartz where many days of aging happen in a few hours - I have MTI260's particularly keen on this trick. I had originally been interested in investigating jumps, but since they were most obvious in the poorer oscillators my interest waned a bit. Doing a search on rubidium frequency jumps turns up a fair bit, although much is on the GPS Rb's which unfortunately will not be cheap surplus any time soon - unless someone really messes up! Angus. From: Hal Murray To: Discussion of precise time and frequency measurement Sent: November 3, 2013 9:28 PM Subject: Re: [time-nuts] The 5MHz Sweet Spot Do low cost recycled Rubidiums have any quirks equivalent to frequency jumps in crystals? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clock Driver Design
Hi, Square wave outputs can be rather higher maintainance, with the whole distribution system from the PCB design and layout through all the wiring to the terminations and beyond all has to be up to the fast IC's/transitions. 10MHz sine waves are much more forgiving. Square waves are useful for some things, but I tend to avoid them like the plague, or immediately turn them to sine, unless I need them. It just depends what it's wanted for. Angus. From: Bob Camp To: Discussion of precise time and frequency measurement Sent: September 27, 2013 12:44 AM Subject: Re: [time-nuts] Clock Driver Design Hi Ok, the SN74LVC1G125 is 35 cents each at Mouser if you buy at least 10 pieces. That's going to be $3.50. LM78L05 is 26.5 cents if you buy 10 pcs. You will need some bypass caps and resistors, I'd assume you already have them. Say you want 10 channels, that's 11 logic id's. At one IC per output that's almost $4 plus the 27 cent regulator. Still under $5 for all the parts. It's roughly $10 if you double up on all the output channels. Do a quickie PCB from any of the usual outfits for $10 or so on a small run / one day turn basis. Total cost without connectors or case $20 in very small quantities. Bob On Sep 26, 2013, at 5:05 PM, John C. Westmoreland, P.E. wrote: SN74LVC1G125 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FE-5680A Loop Lock Indicator
Hi, A lot of indicator outputs on oscillators and other things are completely or primarily pull-downs, just like some microcontroller pins. The problem with surplus stuff like this that don't come with exact datasheets for their options is that you have to work out for yourself how it's configured, etc. If it does not look like a proper TTL or CMOS output (especially when loaded a little) it's worth checking to see if it is a pull down. Sometimes they're just weird (or faulty!). It all depends what they were designed to connect to. I find low current LEDs are useful to give some indication with minimal loading to reduce the chance of any complications, since you never know what else is going on. A while back there was some discussion of the pps output on some 5680As not working because of the lock indicator pin being pulled down too much. More info at http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5680a_faq if you have not already seen it. Angus. From: Bob Stewart To: Time Nuts Sent: September 22, 2013 10:12 PM Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator I hadn't thought of using a pullup resistor. I'd have to get out the calculator to see if it's worth it, though. It's only taking a load for a minute or two till it locks, so I don't think it's a problem. Bob From: Chris Stake To: 'Discussion of precise time and frequency measurement' ; 'Bob Stewart' Sent: Sunday, September 22, 2013 2:06 PM Subject: RE: [time-nuts] FE-5680A Loop Lock Indicator I have a circuit that seems to work well: The lock indicator is a weak source but a good sink so it interfaces more naturally with a pnp or p-channel device. Pull it up to 5V with 100K and connect this point to the gate of a P channel Mosfet whose source is also connected to 5V. Connect the drain of the mosfet to a LED anode and take the LED cathode via 220 R to 0V. This way, the sense of the indicator is correct (0n = lock) and the drive capability of the lock signal works in your favour. Chris Stake -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: 22 September 2013 18:53 To: Bob Stewart; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator Hi If you want 10 ma through the LED (which should be plenty) then the collector resistor would be right around 1.2K Bob On Sep 22, 2013, at 1:32 PM, Bob Stewart wrote: D'oh, that should say I could increase the COLLECTOR resistor to 1500 ohms. From: Bob Stewart To: Discussion of precise time and frequency measurement Sent: Sunday, September 22, 2013 12:27 PM Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator Except that it doesn't work with even 1500 ohms in the base lead. The LED immediately comes on and stays on. I could increase the emitter resistor to 1500 ohms and get around 8.5-9ma through the LED, but I'm done playing with it until I get a proper box to put it all in. This is just a random 3mm LED out of an HP 37203A, so maybe that has something to do with it? I haven't looked at the specs. Bob From: Bob Camp To: Discussion of precise time and frequency measurement Sent: Sunday, September 22, 2013 12:12 PM Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator Hi Circuit should be: 2N with emitter to ground, collector to LED, base to lock indicator via the 4.7K resistor. The LED is hooked to +15 via another resistor. If you have ~ 10 ma in the LED then the base needs less than 0.1 ma to do the job with a . A 4.7K should be plenty. Alternate circuit: 2N with base to lock indicator / no resistor at all, emitter to ground via a 1K resistor, collector to LED. LED to +15 via a 1.5K resistor. Either one should work. Both turn on the LED when the output is high and off when the output is low. In order to turn on when it's high you need to get an inversion ahead of the 2N. Bob On Sep 22, 2013, at 12:17 PM, Bob Stewart wrote: Hi Bob, I tried 4700 and even 1500, but they're too large. I guess the little flash of the LED at power-on is the hint that 1K is right at the ragged edge. It would probably make a big difference if there was a 100 or even 47 ohm resistor between the emitter and the LED, but my little board is starting to get burnt up, wires are starting to get frayed, and it does work, so this cake is done. Bob From: Bob Camp To: Discussion of precise time and frequency measurement Sent: Sunday, September 22, 2013 6:31 AM Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator Hi If you trace out the chip that drives the lock indicator it's got some sort of strange gating in it's supply pin. That gets
Re: [time-nuts] GPS with 10KHz output
Hi, I may have missed something back then, but I don't recall any description of exactly how it was generated - more a discussion of what the manuals/datasheets meant. Angus From: Bruce Griffiths To: Discussion of precise time and frequency measurement Sent: September 19, 2013 8:22 AM Subject: Re: [time-nuts] GPS with 10KHz output Hal Murray wrote: albertson.ch...@gmail.com said: If you ned the 10KHz, Jupiter is one that has been used. I think a 10KHz GPS will make your GPSDO converge quickly ... Does the 10KHz signal change smoothly or does it jump to a new value once per second? Has anybody looked at the fine print? What sort of ADEV is there on the 10 KHz signal? It jumps. We discussed this several months/years ago. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] My GPSDO project: OCXO Thermal Oscillation?
Hi, To be able to test GPSDO's (and GPS in general) was one of the main reasons that I made a temp controlled chassis for an LPRO and gave it air pressure compensation. That was good for tau's of hundreds to tens of thousands of seconds, and even longer with drift compensation. Add in a clean-up oscillator if desired, and you have a pretty good reference. Incidentally, I tested 2 FEI5680A's, a Temex LPFRS and 3 LPRO's in this type of setup, but only the LPRO's allowed the air pressure effects to be almost completely cancelled out. For some reason the others did not react to fluctuating air pressure as predictably. Angus. From: Bob Camp To: Discussion of precise time and frequency measurement Sent: August 16, 2013 7:45 PM Subject: Re: [time-nuts] My GPSDO project: OCXO Thermal Oscillation? Hi With the 5335 you have a measurement with dead time. That makes things a bit hard to figure out. A much better way to go is to feed a pair of 1 pps signals into the 5335 and measure their time difference. Unless they are quite close, you can go for a while with no ambiguity to the reading. The effective resolution increases linearly with the time length of the observation. There also are a number of very nice programs that will let you collect the data from the 5335 via GPIB. Assuming your 5335 works like mine does it's got about a 1 ns resolution at 1 second. It'll give you 1 ppb at a 1 second gate and 1 ppt at a 1,000 second gate. By the time it gets to 1,000 seconds the internal counters have overflowed and the reading is a bit messed up. Without some sort of accurate reference, there's really no way to know for sure what's going on with a GPSDO. One solution is to build two or three of them and watch them fight with each other. Another solution is to pick up a Hydrogen Maser. It's always a what's in your wallet sort of decision. Bob On Aug 16, 2013, at 2:26 PM, Bob Stewart wrote: Hi again Bob, D'oh, I think I totally misunderstood your figures in my first response. The .16ppb is not the frequency accuracy of my GPSDO. It's the amount that I'm moving the OCXO during a 5 minute timeframe, which is something else entirely. Like I said I do not have a known good oscillator to compare to. However, I have a DDS oscillator I made some time ago, and it seems to be pretty stable if I let it be. So, what I've done is to hook the GPSDO to the clock input of my 5335A. I've then adjusted the DDS so that it reads near 10.00 MHz, and watched it over a round-trip 5 minute period several times with a large enough gate that I get 8 decimal points on the counter. I don't see any relationship between the few milli-Hz movement the counter shows and the changes to the DAC. During several runs last night, I saw less than 30 mHz of movement, which, if true, would be 3E-9, or 3ppb, right? Or would that be +/- 1.5ppb? Bob From: Bob Camp To: Discussion of precise time and frequency measurement Sent: Friday, August 16, 2013 10:47 AM Subject: Re: [time-nuts] My GPSDO project: OCXO Thermal Oscillation? Hi Ok, let's try some math and see if I can do it without blinking this time…. +/-4 Hz for 6 volts is 0.66 Hz / V output is 10 MHz so 1 Hz is 0.1 ppm your OCXO is running at 0.066 ppm / V That's also 66 ppb / V 0.02 V at 66 ppb / V is 0.0132 ppb or 13.2 ppt The UT+ has a sawtooth output that's about 45 ns That's 45 ppb at one second 5 minutes is 300 seconds so 45 / 300 = 0.15 ppb or 150 ppt If it's the later clone version it might be about 1/2 of that. Are you doing sawtooth correction? Bob On Aug 16, 2013, at 11:09 AM, Bob Stewart wrote: I'm converting the code for the VE2ZAZ FLL to a PLL. I'm seeing the phase correction change the EFC up and down about .02V to .03V over a period of 5 minutes or so (it varies). The full range on the OCXO is about +/- 4Hz varied by 0 to +6V, so at least this is a tiny value. I feel pretty confident with my code at this point. I'm using a Trimble 34310-T OCXO for which I've been able to find almost no information. Could this oscillating phase correction be some sort of thermal oscillation? I've tried two separate 34310s and both act more or less the same. My GPS device is normally a UT+, but I just now swapped in an Adafruit Ultimate GPS Breakout to the same effect. Is this good, bad, or indifferent for a GPSDO? I started this project not knowing what to expect, and I still don't. Experienced help, speculation, or even just kind words at this point would be appreciated! =) I don't have a known good/stable reference to compare this to. Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions
Re: [time-nuts] Rb video
Hi, In this case the fan is the primary cooling method. The heatsink may help a bit, but the fan appears to have done most of the work since the base is not that hot even without the heatsink. For testing the 5680's I got on their PCBs, I just had a tiny fan on standoffs stuck on top of them which cooled the whole thing well. Angus From: Magnus Danielson To: time-nuts@febo.com Sent: August 10, 2013 12:01 AM Subject: Re: [time-nuts] Rb video On 08/09/2013 03:09 PM, Bob Camp wrote: Hi A few observations: 1) He talks about using a heat sink on the front panel, but then never shows it / does it. The fan inside the box is not going to cool that Rb the way it needs to be cooled. You either need a pretty massive heat sink on the front panel with no fan or something smaller with moving air. He actually says that he was unable to get it in time as it was on back-order, so he could not show it mounted, so he showed everything else. The cooling fan is to make enough air circulate to keep the PSU cool enough, considering that the rubidium gets hot, but the cooling fan is not the primary cooling method for the rubidium. He do understand the cooling needs of the rubidium, but I would let there be an active control-loop for the fan cooling the rubidium. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] RS 232
Hi, #5 is one of the reasons I preferred not to take the signal negative. I suppose it depends on the situation, but for the spitting data into a pc I used to find that a 0 to 5v or so signal powered from a control line almost always worked. The most common problem was either a faulty com port or an optocoupler circuit that did not have enough gain to pull the line close to 0v. ( that was a while ago though - not so much 'legacy' as 'vintage'! ) Angus. From: Bob Camp To: Discussion of precise time and frequency measurement Sent: July 26, 2013 1:37 PM Subject: Re: [time-nuts] RS 232 Hi In order to get voltages from the other pins on the D connector: 1) You have to program them to be in the correct state (either high or low) 2) They have to be present on the driver side (usually, but not always true) 3) They need to be 3 V (diode drops etc…) 4) They need to supply enough current (as in no isolating resistors, usually true) 5) You need to have two of them to spare that meet these criteria (one positive and one negative) Its a little like rolling dice, sometimes it will work, sometimes it won't work. Bob On Jul 26, 2013, at 7:01 AM, ewkeh...@aol.com wrote: Since there is repeated request for the circuit se attachment. My question is what can be done to get a positive voltage from some of the other unused pins of the DB 9 connector. What is needed is any where from 3 to 15 volt. Diodes work with 1 mA but I set Rx for 2 mA. Any thing else look at H11 data sheet. Bert Kehren In a message dated 7/26/2013 4:06:37 A.M. Eastern Daylight Time, r...@sonic.net writes: FWIW, it was clear as mud for me too. Bert began with, Since joining time nuts over four years ago I have not used a single MAX 232 chip. Two reasons MAX do not give me isolation and do generate noise in critical applications. From that I took that he was doing RS232 using opto isolators. That implies + and - voltages to me. Where do they come from and where are they relative to the isolation boundary? If the goal is really isolation, how do these supplies get isolated? If the noise is cured by isolation, these details seem important as the supplies need isolation too. Maybe the switcher in the MAX232 is causing the noise. Then how do we get a negative supply from, say, +5V without the noise? Then, maybe he was saying RS232 sucks and this other way (not RS232 compatible) works better. The word picture of Bert's solution, which provided more details, left me less much less than clear too. Maybe I'm just not up on circuit shorthand terminology enough to follow what sort of current limiter is limiting what current to what, and what is being blocked by a diode from which negative level. Not really sure if I even got the big picture of what he is describing. Is it an isolated equivalent of a MAX232 interface or something else that wouldn't talk to an RS232 device? So, more clarification, or possibly that picture (~= 1k words) might help. Or maybe I'm just obtuse and everyone else is getting it. (Seems Marki may also be in the confused camp.) On 7/25/2013 3:34 PM, Mark C. Stephens wrote: Although your description, I prefer the use of two H11 opto couplers which work perfect. On the receiving end the diode along with a current limiter and blocking diode for the negative level works perfect. On the output side a power source is needed. Is a perfect circuit description, I'd be more confident with a schematic :) --marki -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of ewkeh...@aol.com Sent: Friday, 26 July 2013 5:32 AM To: time-nuts@febo.com Subject: Re: [time-nuts] RS 232 I do not understand your question, I am referring to low noise applications like counters for dual mixers or other AV measurements, but also Shera and even Tbolt where external noise should be kept to a minimum. When you chase 1 E-14, isolation is key and I always like to err on the cautious side and as I stated we use blue tooth or USB but in the case of USB there are always H11 in the circuit. Some still like to use RS 232 and the subject came up and I have on my boards H11's like on the counter Corby uses but he ended up using an external power source and I like to eliminate that requirement. David had the right answer using the power that the RS 232 mouse uses out of a DB 9, started looking but I do not have one any more and I can not find any data. Bert In a message dated 7/25/2013 2:48:43 P.M. Eastern Daylight Time, ma...@non-stop.com.au writes: Hi Bert, I am sure your circuit is clear in your head, but would you mind attaching detail? You have perked my interest with the low-noise keyword ;) -marki -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun
Re: [time-nuts] Cheap 9.8Mhz Sa.22c's
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Re: [time-nuts] LPRO 101 ADJUSTMENT
External adjustment makes it very easy to adjust as you have access to the adjustment voltage to measure it, and even a 1K multi-turn wirewound pot would give around 1E-12 setting resolution. The sensitivty of the EFC is only around 1E-12 per mV, so it is much less sensitive to temperature stability than quartz oscillators. A temperature coeff of +/- 20ppm /degC with an EFC voltage of 2.5V would only contribute around +/-5E-14 /degC frequency change. By adding fine adjustment or a DAC, you can get way below 1E-13 setting resolution. The only problem here is that environmental conditions such as variations in temperature and pressure do affect Rb oscillators and the EFC circuit, and can change the frequency by 1E-13 in a matter of minutes. Still, it's useful to be able to do it for disciplining, or if the environmental conditions are being controlled or compensated for. The ADEV of an LPRO can be around 1E-13 or so at a tau of hours, so even a step size of 1E-13 can be rather too coarse, especially if the environmental effects have been minimised. It would be nice to find a relatively simple and inexpensive 10MHz synthesizer that has a resolution of closer to 1E-14 to avoid messing with the EFC at all. Angus. On Fri, 25 Jul 2008 20:33:26 -0400, you wrote: If I choose to control the frequency via External C-field control I guess it would take a very precise and stable voltage source. Any thoughts or suggestions? - Original Message - From: Scott Mace [EMAIL PROTECTED] To: jshank [EMAIL PROTECTED]; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, July 25, 2008 7:15 PM Subject: Re: [time-nuts] LPRO 101 ADJUSTMENT Both methods work well. Be sure the unit is mounted to some sort of heatsink,chassis, etc. I'm using a Fury GPS receiver to drive the EFC on an LPRO-101. You won't get much range out of either adjustment. Leave it powered on for a couple of hours before trying to adjust it. I usually set the trim pot in the middle of it's range and use the EFC pin. I think it's a 28 or 30 turn pot. EFC is 0-5v. The unit will self-bias to around 2.5v if the EFC pin is open. Scott jshank wrote: Hi, I recently acquired a LPRO 101 Rubidium Oscillator. After reading the manual I see that there are two ways to adjust the frequency 1) using and adjusting screw on the unit and 2) using the External C-field control signal at pin J1-7. Has anyone experimented with either method and if so what method was preferred? Jeff ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Double ovened 10811-60158 on ebay
I see that the same vendor has a few more units for sale. He has also included a picture that labels all the connections. At least they look to be complete with their outer covers now, which would be useful if anyone did want to add some temp control. Seeing all those oscillators does make me wonder what they came from - a heap of working 58503's going to landfill is close to sacrilege :-) Angus. On Sat, 12 Jul 2008 11:20:57 -0600, you wrote: Message: 2 Date: Wed, 9 Jul 2008 12:10:52 +1000 From: Jim Palfreyman [EMAIL PROTECTED] Subject: [time-nuts] Double ovened 10811-60158 on ebay To: time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1 Sorry to pollute the list but some people here may be interested and I think this might be a good buy. Ebay item 250268030266 a bunch of 10811-60158 wrapped up in a second oven that have been pulled from a bunch of HP 58503A. There are 21 units available at US$50 Buy It Now. Postage seems reasonable too. I've bought one and so if anyone knows where I can get the cabling requirements please let me know. Regards, Jim Palfreyman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] FTS 1000B instability problem.
Hi, I have a problem with an old FTS 1000B from around 1993/4, and am wondering if anyone here has any suggestions or can point me to any info. The problem is just that it's much less stable than it should be - at 100s it's around 1E-11. As well as general instability, it often drifts by 6 to 10 E-11 over half an hour or so, often drifting back by the same amount a while later. (At 1s it's worse than it should be, but not by very much, and long term aging is ok) The control/ref voltages on the buffer board are stable, as is the oven temp. It's on a stable linear supply which has worked fine with any other oscillator that I've tried on it, even if connected at the same time as the 1000B - although each with its own filter. I have a horrible feeling that it's just the crystal slowly dying, but hopefully it's less terminal. Thanks, Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Comparing Reference Accuracy
On Fri, 23 May 2008 09:26:43 +1200, you wrote: The errors of the various GPSDOs cannot be determined without access to a primary standard. Has anyone here tried to squeeze extra medium term performance out of a rubidium by controlling (or compensating for) environmental factors like temperature and pressure? Not having a decent reference for testing GPSDOs was one thing that made me want to see what could be done, although I'd been wanting to try it for a long time anyway. I recently got around to testing an LPRO against GPS, and the stability was still a fairly useful 1E-13 at 1 day. It was in a temperature controlled housing, and had an analogue pressure sensor connected up to it to adjust the c-field to compensate for air pressure changes - not a perfect setup, but as an experiment it was definitely promising. I'm not suggesting that it would be as good as a primary standard, but it could be useful in some circumstances, either stand-alone or steered to GPS. The only paper I came accross which deals specifically with this is a rather short one where FE5650A's were tested: The Effects of Ambient Temperature Fluctuations on the Long-Term Frequency Stability of a Miniature Rubidium Atomic Frequency Standard Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Which HP Frequency Counter?
A lot depends on the resolution you need and what all you want to use it for, but it might also be worth looking at some recent Fluke counters. The PM6681 has a nominal rating of 300MHz on it's main input, although it may read rather higher. It has 1M or 50R input res, and can tolerate up to 12V rms. Also, its nominal time interval resolution of 50ps single shot and 1ps averaged can be quite useful. The PM6680B is only rated at 225MHz, but it's cheaper, and sometimes turns up with a high frequency channel at a reasonable price. GPIB was an option with this one, so if you want that, you would have to check that it's fitted. It might also be worth checking if a separate prescaler would be ok for your high frequency use, rather than having to find (and pay for) a counter with a high freq input. An active probe could be used to reduce the loading, but they tend to be expensive to buy. Sometimes an HP53131A also turns up at a decent price, but probably not with a high frequency channel. Input damage level is quoted at 5V rms for it. Personally, I really like the PM6681 since it's so capable, and I find it much easier to use if the settings have to be adjusted much - but the HP has an RS232 port which makes logging the data very simple on any computer. Angus. On Sat, 08 Mar 2008 17:49:02 +0100, you wrote: Dear group, I consider buying a used lab frequency counter / timer --preferably HP/Agilent-- covering from few mHz to perhaps 400 MHz. I'm worried that models handling high frequencies seem to be limited to under 100 mV input signal max. I don't want to destroy an input channel each other day when calibrating/repairing some instrument. Also are there instruments with high impedance input? 50 Ohm is not quite right for investigation in the guts of most designs. Is it possible to find a not-too-old model under $800? I would like to find something in France or UK or Europe, but it seems hopeless in this budget. I would favor a repairable model (with available service docs schematics). Your expert advises are more than welcome! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Allan variance Vs Plain Old Accuracy
On Thu, 14 Feb 2008 11:00:32 -, you wrote: Hi All, This comment is bound to get you all going. Maybe I'm being stupid, but why does everyone use Allan Variance and not plan old accuracy? I am very familiar with David Allan's full article on Allan Variance. However Allan Variance isn't the same as accuracy. Accuracy is what is important to most people. And that's not RMS but peak to peak, e.g worse case. And not averaged over 24 hours but averaged over 1 second or less. Something I rather miss is some good old phase or frequency plots - especially if done at different timescales - which seem to be becoming rather less common now. As well as having a plot of ADEV or its relations, seeing what the reference is doing and when is useful, and most ADEV plots using so few values of tau does not help. Angus. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] means of calibrating/verifying Ru with GPS
On Sat, 22 Dec 2007 22:02:49 +1300, you wrote: swingbyte wrote: Hi everybody, I mentioned some time ago that I had an Ru 10MHz source and I would like to calibrate it. I have an hp 5335 counter and a Jupiter GPS with 10kHz output. I was wondering if I could use the Ru 10MHz as and external clock for the 5335 and then measure the frequency of the 10kHz gps locked signal and adjust the Ru to read exactly 10kHz? If I let the 5335 average the frequency input it will display 12 digits - how many of those are reliable I'm not sure but it seems that this may be an easy way for me to check the Ru. Is this a viable method or am I missing something - I haven't done a lot of research into the time keeping world yet. Also, the model Ru I have is the Efratrom frk-h with external frequency control. I have had a quick read of the manual but can't find any information on how this works. I was thinking this might enable me to discipline the Ru to GPS - does anyone know how this works? Thanks for your help Happy holidays Tim Tim The biggest problem with your proposed measurement scheme is that the 10kHz signal is no more stable than the PPS output. The 10kHz output is phase jerked every second to realign it with the UTC second. This behaviour is clearly documented in the receiver datasheet. All the docs I've seen are rather functional in their description, and short of detail. I was curious how exactly the 10KHz is generated, how it's aligned, and the precision/position of each rising edge - anyone got any info on this? Thanks, Angus. Thus to reduce the measurement error due to this instability to better than 1E-10 or less the counter gate time will need to be around 1000 seconds or more. Adjustment to better than 1E-10 will be somewhat problematic not to say time consuming. Fortunately the 5335A maximum gate time is 1E7 seconds or about 4 months, so this may actually be possible. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS: ADEV or MDEV?
The VP is still distinctly worse until tau 1000sec. The plots are not conclusive evidence that correcting for the sawtooth error isn't advisable. What about hanging bridges and similar artifacts? Bruce It would be interresting to see exactly how much the sawtooth on an M12 affects actual GPSDO setups. I made a hardware sawtooth remover a couple of years ago as an experiment, but where I used it I didn't seen much difference. I just checked again recently, but the sawtooth errors seem very small compared to overall instability, even for just an M12 to Rb at a fairly stable temperature. The larger errors of a few ns (over 1000s) which are occasionally visible when the M12 is temperature controlled seem regularly to be exceeded by other instabilities in the pps output. There are plenty of times when sawtooth removal would be of use/interest, but in a typical GPSDO which has a heap of other errors, I do wonder what improvements in performance would actually be seen in the output from the oscillator - which is all that a lot of people are really interrested in. Angus. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Frequency counter recommendations
Hi, Although they are rather less common and more expensive than the ones you mentioned, Fluke/Philips 6681 counters are also very good. Nominal resolution is 50ps single shot and 1ps repetitive. No RS232, but GPIB and a rather basic analogue output are standard. On Mon, 19 Mar 2007 22:24:46 -0800, you wrote: Hi all, I have a run-of-the-mill frequency counter (8 digits, 0.1 and 1.0 sec gate, no reference oscillator output or ext. input) and would like to upgrade to something better. I would initially like to measure frequencies in the 10 MHz or below range with a resolution of better than 0.1 Hz. From reading this list have picked out a HP 5334 or a Racal-Dana 1991/1992. Some of these have been recently on ebay, but that is not my preferred source, the seller often does not state the options installed, as well as the typical ebay problems. Are there others someone would recommend, used? -Dave D. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Thunderbolt versus Home made
On Sun, 25 Feb 2007 09:52:55 -0600, you wrote: Angus wrote: Although that's not what I was talking about doing above, I think that it's pretty much what some of the hardware GPSDO's actually do using various types of oscillators (and to good effect too). As in these: http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm http://www.frars.org.uk/cgi-bin/render.pl?parameter=pageid=1285 the loop filter is basically just an RC circuit. It's not quite raw GPS, but is quite different to using a digital filter as used in a Thunderbolt, Shera, etc., which can run to hours. When the N1JEZ board was mentioned, I assumed that it was this type of controller that was meant - and I think it does need 10KHz unless it gets much more of a mod than a couple of counters. Angus. Angus, Don't get me wrong, the James Miller design does a great job, considering it's simple and elegant implementation and the fact that for so little money you can have a frequency standard that beats anything a ham could make in his or her shop. This will do a great job for most applications where you want to be within a few Hz or so around 10 GHz, and as long as the GPS signals are good. For the intended market, if the GPS signals are not good, you simply wait or move the antenna. A lot of the money spent on commercial GPSDO's is spent on improving hold-over performance, because many commercial applications simply cannot postpone using the system until the GPS signal is good. I just wanted to point out that the 10 kHz output can be misleading. The GPS timing is such that if you have a quality OCXO, a loop faster than at least 20 minutes will actually do a disservice to the OCXO, regardless of the PLL reference frequency. If you use an inexpensive, not temperature stabilized VCXO, you can probably speed up the loop quite a bit, simply because the VCXO itself in free running mode will not be doing that great. If your frequency and time needs are modest (and that probably covers 99% of applications, including anything I could dream of personally), this design will be perfectly satisfactory. But, and this is a significant caveat, this is TIME-NUTS where most people are looking at that like the holly grail 1% :-) Didier Hi Didier, Sorry, my original post was not very clear - I had only wondered if faster PPS signals might ever help with the measurement each second; I didn't mean to suggest that they might affect the required overall loop time much. ( Thinking back to all the posts a couple of months ago, I should probably resist any urge to comment on the effect of sawteeth on stability for the moment... ) Anyway, I was just curious. It's one of the many things I don't have much time to mess with, so wondered if anyone else had - but apparently not. Angus. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Thunderbolt versus Home made
On Sat, 17 Feb 2007 08:50:56 -0600, you wrote: Angus wrote: On Fri, 16 Feb 2007 17:44:14 -0600, you wrote: Richard W. Solomon wrote: I looked at the ACE-III on Trimble and do not see mention of a 10 KHz output. Maybe I miised it, but without it, the N1JEZ board will not do unless you modify it for 1 pps. I am trying to find more info, but since it reached EOL, Trimble may have deleted it. 73, Dick, W1KSZ Dick, You are correct, you need to patch another set of dividers in the chain. Keep in mind that the only benefit of a 10 kHz output on the Jupiter is to save 4 decade dividers. You should not use the fact that the Jupiter outputs 10 kHz to speed up the loop in a GPSDO. The loop bandwidth is a function of the crossover point between the VCXO and the GPS, which in most cases will be between many minutes (cheap VCXO) and a few hours (HP 10811). Whether you use 1 Hz or 10 kHz comparison frequency into the phase detector will not affect the filter. Hi, (As this is my first post here, I'll try not to mess up too badly :) I think that for a simple controller like the N1JEZ board, a 10KHz output on the GPS really is needed. I tried a circuit like that with 100pps once out of curiosity, but as I remember, the lower error sensitivity made things more difficult. BTW, with a standard GPSDO, would using the 100Hz/10KHz the pulse not reduce the need for a fast comparator clock, and also reduce sawtooth effects? Angus. Angus, One of the problems with the 10 kHz output us that it is only updated once per second, i.e. the period of the 10 kHz signal is the same for 1 second, and every second, there is a small phase jump to update the phase of the 10 kHz to match the 1 PPS. I don't know whether the outputs on a Jupiter exhibit any granularity or not (I've not seen anything to suggest that they do), but I think that with receivers that do, changing from 1PPS to a faster PPS output would normally change the granularity effects that are seen - assuming things are not in sync. As for possibly reducing the need for a fast clock; being able to measure a number of pulses in a second and then take the average count can allow a rather better resolution than just taking one measurement - so in some circumstances this could be useful. I've not really looked into it much, but was really just interrested if anyone here had come accross the 100/1K/10K, etc pulses being used like that. That means the 10 kHz has a one Hz component that is the correction signal. It must be filtered out. But even filtering the 1 Hz component is not sufficient, since the 1 Hz component has the same short term noise that is present on the 1 PPS output of any GPS receiver. So while it's a lot easier to filter 10kHz down to a level where 10 kHz ripple does not appear on the OCXO EFC input, such a filter would be grossly insufficient to make a GPSDO. You would simply have an OCXO phase locked to a poor reference. Although that's not what I was talking about doing above, I think that it's pretty much what some of the hardware GPSDO's actually do using various types of oscillators (and to good effect too). As in these: http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm http://www.frars.org.uk/cgi-bin/render.pl?parameter=pageid=1285 the loop filter is basically just an RC circuit. It's not quite raw GPS, but is quite different to using a digital filter as used in a Thunderbolt, Shera, etc., which can run to hours. When the N1JEZ board was mentioned, I assumed that it was this type of controller that was meant - and I think it does need 10KHz unless it gets much more of a mod than a couple of counters. Angus. You must filter the output signal from the phase comparator so that the short term instabilities in the GPS timing signal are also filtered out. The 10 kHz is useful for experimentation, since you could artificially speed up the loop with one second or so time constant or even less so that you could easily verify with an oscilloscope that the OCXO is actually phase locked to the GPS, but you would not want to run the system that way because it would have terrible performance. With a time constant of 20 minutes to an hour, it can be very frustrating to verify that the system phase locks and it would be best to have another hobby to attend to in the mean time :-) Regarding the sawtooth effect, since the 10 kHz is only updated every second, it has no effect on the possibility of hanging bridges, and I am not sure what you mean by reducing the need for a fast comparator clock. Didier ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Thunderbolt versus Home made
On Fri, 16 Feb 2007 17:44:14 -0600, you wrote: Richard W. Solomon wrote: I looked at the ACE-III on Trimble and do not see mention of a 10 KHz output. Maybe I miised it, but without it, the N1JEZ board will not do unless you modify it for 1 pps. I am trying to find more info, but since it reached EOL, Trimble may have deleted it. 73, Dick, W1KSZ Dick, You are correct, you need to patch another set of dividers in the chain. Keep in mind that the only benefit of a 10 kHz output on the Jupiter is to save 4 decade dividers. You should not use the fact that the Jupiter outputs 10 kHz to speed up the loop in a GPSDO. The loop bandwidth is a function of the crossover point between the VCXO and the GPS, which in most cases will be between many minutes (cheap VCXO) and a few hours (HP 10811). Whether you use 1 Hz or 10 kHz comparison frequency into the phase detector will not affect the filter. Hi, (As this is my first post here, I'll try not to mess up too badly :) I think that for a simple controller like the N1JEZ board, a 10KHz output on the GPS really is needed. I tried a circuit like that with 100pps once out of curiosity, but as I remember, the lower error sensitivity made things more difficult. BTW, with a standard GPSDO, would using the 100Hz/10KHz the pulse not reduce the need for a fast comparator clock, and also reduce sawtooth effects? Angus. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
